Byron Shaw
Peter Amtsen
William VanRyswyk
University of Wisconsin- Stevens Point
Acknowledgements
Many individuals were involved in the executionof this project. F:undingfor
the project was provided by the WisconsinDepartmentof Natural Resources,
University of Wisconsin ResearchConsortium, and University of Wisconsin-Stevens
Point EnvironmentalTask Force Program (ETF).
We want to thank the following staff and studentsfor their supportand
assistancein conductingthis project:
Richard Stephens,JamesLicari, KandaceWaldmann, and William DeVita
(ETF) for coordinating the laboratory analysisof all the water samplescollected.
NancyTuryk andDebraSisk(ETF) for reportpreparation,graphics
developmentand data entry.
Christine Mechenich, Central Wisconsin GroundwaterCenter, for coordination
and assistancewith the homeownersurvey.
Fred Madison, Wisconsin Geologicaland Natural History Survey for
assistancewith project planning, well installation, and ground penetratingradar
surveys.
Eric Harmsen, University of Wisconsin-MadisonAgricultural Engineeringfor
cooperativework on this researchproject.
Jeff Shaw for developmentof the GIS for this project.
i
Abstract
The impact of subdivisionson groundwaterquality has becomea topic of
interest throughout the United States,as interest in groundwaterprotection has
increased. Developmentof unseweredsubdivisionsadjoining municipal areashave
increasedas urban populationsexpandand people seeksuburbanareas.
This study was initiated in 1987in an attempt to quantify the impacts of
subdivisionson groundwaterquality in the Central Sandsarea of Wisconsin. The
project involved the installation of over 200 monitoring wells in and around two
subdivisions. Thesewells were sampledand analyzedfor a variety of chemicalsover
a four year period. Nitrate-N loading to groundwaterwas the primary focus of the
project, with volatile organic chemicals,phosphorous,and severalother indicator
chemicalsrun on selectedsamples.
Homeownerswere surveyedto determinehouseholdand lawn chemical use,
and to obtain their opinions on groundwaterquality. A number of individual septic
systemswere monitored, as were severallawns, to obtain data specific to these
practicesthat impact groundwaterquality. A Nitrogen Mass Balancemodel was used
to test its capabilitiesto predict subdivisionimpacts.
Resultsof this project clearly demonstratedthat subdivisionson sandy soils do
impact groundwaterquality with nitrate-N levels exceeding10 mg/!. Chloride,
phosphorous,sodium, and limited volatile organic chemicalswere also found in
elevatedconcentrationsdowngradientof the subdivisions. Septic systemscontributed
approximately 80 percent of the nitrate-N to groundwaterfor the areasstudied, with
lawns contributing the remaining 20 percent. Lot sizesin thesesubdivisionwere
approximately0.16 hectare,with about three homesper hectareincluding roads,
vacantlots, and open areas.
The BURBS massbalancenitrogen Loading model provided good estimatesof
groundwaterimpacts from subdivisions.
Extensivewater quality differenceswere observedwithin and downgradientof
the subdivisions. Contaminantplumes from septic systemsmixed slowly with
groundwater,which resultedin dramaticvariability of water quality both vertically
and horizontally downgradientof the subdivision. This wide variability makesit very
difficult to measuregroundwaterimpactseven when a large number of multi-level
wells are used. Variability seasonallyand from year to year was observedin shallow
monitoring wells, respondingto relative amountsof groundwaterrecharge.
The presenceof relatively undiluted contaminantplumes 30 meters
downgradientof septic systemsmakesit extremely important to be certain private
wells are not located in a groundwaterflow path from drainfields, or that they are of
sufficient depth to avoid the contaminantplume.
ii
Table of Contents
Acknowledgements
Abstract
Table of Contents
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii
List of Tables. . . . .
iv
List of Figures
VI
A. Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1
SandPlainGeology. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3
3
4
11
13
18
22
22
23
25
B.
Literature
Review
Subdivisionsand Nitrate-N
.............................
SepticSystemsandGroundwater
Quality. . . . . . . . . . . . . . . . . . . .
Nitrogen. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Phosphorus.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Bacteria. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ChloridesandOtherPotentialContaminants. . . . . . . . . . . . '. .
LawnStudies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PreviousStudies
in theProjectArea. . . . . . . . . . . . . . . . . . . . . . .
C. Methods
Surveyof Homeowners
MonitoringWell InstallationandDesign. . . . . . . . . . . . . . . . . . . ..
28
28
30
Groundwater
Sample
Acquisition.. . . . . . . . . . . . . . . . . . . . . . ..
42
InorganicChemicalAnalysis. . . . . . . . . . . . . . . . . . . . . . . . . . ..
43
Organic Chemical Analysis
44
D. Surveyof Homeowners
ChemicalUseandAttitudes. . . . . . . . . . . . . . 46
Introduction.
.....................................
46
. . . . . . . . . . . . . . . . . . . 49
49
HouseholdMaintenanceProducts. . . . . . . . . . . . . . . . . . . . . 52
Knowledgeabout Water Suppliesand Septic Systems. . . . . . . . 53
Attitudes
andOpinions
aboutGroundwater
Issues.. . . . . . . . . . 59
60
Relationshipsof Attitudes to Age, Genderand EducationalLevel.
67
Survey Conclusions
68
Survey
HouseholdCleaningProductsUse.
Results
Lawn
.
and
and
Discussion
Garden
Chemical
Use
iii
E. Nitrogen Mass Balance Prediction using BURBS Model. . . . . . . . . . . . 70
Simulation
Results. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
82
Simulation
for HeavierTexturedSoils. . . . . . . . . . . . . . . . . . . . . . 86
VariableDefinition
F. Nitrogen and Water BudgetResultsfrom Field Data
89
G. Comparisonof the Resultsof the Nitrogen and Water Budgets
Detennined
......................................
H. GroundwaterQualityDowngradient
of Subdivision. . . . . . . . . . .
92
94
I. Impact of Lawns on GroundwaterQuality . . . . . . . . . . . . . . . . . . . . 102
J. SepticSystemResearchSiteResults. . . . . . . . . . . . . . . . . . . . . . . .
105
Detailed Septic SystemsInvestigation. . . . . . . . . . . . . . . . . . . . . . . 108
K. PhosphorousImpacts
L.
Variability of Groundwater Chemistry
Downgradient of Subdivisions Relative to Land Use
. . . . . . 115
M. Water ChemistryChangesOver Time Downgradientof Subdivisions. . .
N. Geophysical
Techniques.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
O. TraceOrganicChemicalInvestigation.. . . . . . . . . . . . . . . . . . . . . .
127
Other Organic Chemicals
129
Potential Sourcesof the DetectedOrganic Compounds. . . . . . . . . . . . 130
P. Conclusions.. . . . . . . . . . . . . . . . . . .
Q. Literature
Cited
APPENDIX A
GroundwaterWell Chemistry
. . . . . . . . . . . . . . . . . . . . . . . . . . . A-I
APPENDIX B
BURBS Simulation Characteristics
APPENDIX C
Homeowner Survey
** Appendicesare not included with most copies,
iv
. . . . . . . . . . B-1
List of Tables
1. Summaryof field studiesof nitrate-Nmovementfrom septicsystemsin
groundwater.
2. Summaryof field studiesof phosphate
movementfrom septicsystemsin
groundwater.
3. Numberof usersandaverageuseratesfor householdcleaningproductsin
two PortageCountysubdivisions.
. . . . . . . . . . . . . . . . . . . . . . . ..
4.
5.
6.
7.
8.
Useof selectedmaintenance
productsin two PortageCountysubdivisions...
Lawn carepracticesreportedin two PortageCountysubdivisions.
Problemsresultingfrom groundwatercontamination
in PortageCounty. . . ..
Response
to surveyopinionstatements.
. . . . . . . . . . . . . . . . . . . . . . ..
Relativeamountof turf, naturalandimperviousareasin the BURBS
simulationfor the JordanAcresandVillage Greencuttings. . . . . . . . ..
Q
-. Valuesfor the variablesusedin the BURBSsimulationfor JordanAcres
andVillage Green.
10. BURBSsimulationresultsfor the JordanAcresandVillage Green
cuttings.
11. Resultsof nitrogenandwaterbudgetcalculationsbasedon field data
obtainedfrom JordanAcresandVillage Greensubdivisions.
12. Nitrogenandwaterbudgetresultsfor JordanAcresandVillage Green
cuttings. Resultswerecalculatedusingboth the BURBScomputer
program and actual field data.
13. Average groundwaterchemistry data from wells primarily impactedby
18
22
50
52
56
63
65
75
81
83
90
92
lawns.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
14. Chemistry data from two wells monitoring the groundwaterupgradient
(REE-LU) and downgradient(MCD-LD) of an intensively managed
lawn in Jordan Acres.
15. Average groundwaterchemistry of wells in contaminantplumes
originating from nearby septic systems.
16. Summaryof organic chemicalsdetectedin groundwatermonitoring well
samplesbetweenOctober 1988 and April 1989.
103
106
128
v
List of Figures
1. Upgradientland usesandlocationsof the subdivisionstudysitesin Portage
County,Wisconsin.
,.2
2. OriginalSubdivisionprojectmultiportmonitoringwell design.
32
3. JordanAcresmonitoringwell network,showingthe locationof multilevel,
septic, lawn and survey monitoring wells. . . . . . . . . . . . . . . . . . . ..
4. Village Green monitoring well network, showing the location of multilevel,
33
septic,lawnandsurveymonitoring
wells. . . . . . . . . . . . . . . . . . . ..
34
5. Designof 23 meterdeepmultiportmonitoringwells.
6. Locationof wells at JordanAcressepticstudysiteREE. . . . . . . . . . . . ..
7. REC andREW well design,includesshallow,mediumanddeepports,
located4.6 m downgradient
of the siteREE drainfield. . . . . . . . . . . ..
8. Crosssectionalview of RSDSwells, view is from downto upgradient.
Wells are located38 metersdowngradient
of the drainfield at siteREE. .
9. Designof KEP well, downgradient
of site BAR in Village Green.
10. Numberof participantsreportingvariousdisposalpracticesfor paint
thinner,paint stripperandmotoroil in two PortageCounty
subdivisions.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..
11. Frequencyof lawn fertilizer usein two PortageCountysubdivisions.
12. Type andamountsof insecticidesusedin two PortageCounty
36
39
39
41
42
53
55
subdivisions.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 58
13. Participant responsesabout the major sourceof groundwater
contamination
problemsin PortageCounty. . . . . . . . . . . . . . . . . . ..
61
14. Reasonsgiven by participantsthat groundwatercontaminationis a
"serious" or "very serious" problem in two PortageCounty
subdivisions.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 62
15. Map of JordanAcressubdivisionsub-studyareashowingwell locations. ..
16. Map of Village Greensubdivisionsub-studyareashowingwell locations. ..
17. Watertableelevationmeasured
from the JordanAcresnorthwestsurvey
well, andprecipitationmeasured
at the StevensPoint,Wisconsin
73
74
wastewater
treatment
plantfrom 1987to 1991.. . . . . . . . . . . . . . . ..
76
18. BURBSestimatednitrate-Nconcentrations
relatedto varyinghousing
densitiesat JordanAcresandVillage Greensubdivisions.
19. BURBSestimatednitrate-Nconcentrations
relatedto varyinghousing
densitiesin heavysoilsusingVillage Greensubdivisionvariables. . . . ..
20. Averagechlorideto sodiumratioswith depthin groundwaterfrom
downgradient
wellsat VillageGreen.. . . . . . . . . . . . . . . . . . . . . ..
85
87
96
21. Averagechlorideconcentrations
with depthin groundwaterfrom
downgradient
wellsat VillageGreen.. . . . . . . . . . . . . . . . . . . . . ..
97
22. Averagesodiumconcentrations
with depthin groundwaterfrom
downgradient
wellsat VillageGreen.. . . . . . . . . . . . . . . . . . . .'. ..
23. Averagerelativefluorescence
with depthin downgradient
wells at Village
Green.
vi
97
98
24. Average phosphateconcentrationswith depth in downgradientwells at
Village Green.
25. Average nitrate-N concentrationswith depth in downgradientwells at
Jordan Acres.
26. Average chloride concentrationswith depth in downgradientwells at
Jordan Acres.
27. Average relative Fluorescencewith depth in downgradientwells at Jordan
Acres
28. Average phosphateconcentrationswith depth in downgradientwells at
Jordan Acres.
29. Plot of groundwaternitrate-N concentrationsvs time for wells REE-LU
and MCD-LD in JordanAcres. REE-LU well is upgradientof a lawn,
MCD-LD is downgradientof the lawn.
30. Nitrate-N concentrations(mg/1)in wells S2-22, ENG-SDC, MCD-SD,
and ZAK-SD, located downgradientof septic systemdrainfie1ds. . . . . . .
31. Location of wells at Jordan Acres septic site REE, with average
nitrate-N concentrations(mg/1).
32. Average nitrate-N concentrationsin RSDS multilevel wells 38 meters
downgradientof the REE drainfield.
33. Watertab1eelevationsas measuredin well REC-Medium. . . . . . . . . . . . .
34. Nitrate-N concentrationsfor REC-Shal1ow,Medium and Deep ports. . . . . .
35. Well REW located 4.9 metersdowngradientof a drainfield. Nitrate-N
concentrationsincreasein May, June, July and August correspondingto
irrigation well pumping resulting in changesin the plume configuration. .
36. Profiles of averagenitrate-N concentrations(mg/l) in wells located
downgradientof the subdivisions. View is generally perpendicularto
groundwaterflow.
37. Map showing land usesof Village Green subdivision.
38. Map showing land usesof JordanAcres subdivision.
39. Nitrate-N concentrations(mg/1)of well N4 in Village Green, 1987 to
1991.
40. Nitrate-N concentrations(mg/l) of well S4 in Village Green, 1987 to
1991.
98
100
100
101
101
104
107
108
109
110
111
111
116
117
118
121
122
vii
A. Introduction
Concern over the impact of subdivisionson groundwaterquality has been
growing for a number of years. Increasedincidenceof high nitrates in private wells,
concern over wellheadprotection, and an awarenessof groundwaterprotection have
allIed to this widespread
concern. PortageCounty,Wisconsinhasworkedon a
groundwatermanagementplan since 1985. One of the most controversialparts of the
plan has been the use of increasedlot size to protect groundwaterfrom onsite waste
disposal. This may improve groundwaterquality, but results in more expensive
housing and all the problems associatedwith urban sprawl.
This study was initiated in 1987 to addressthe subdivision water quality issues
and attempt to quantify the impacts of subdivisionson groundwaterquality in sandy
soils areasnear StevensPoint. This project was directed by Dr. Byron Shaw with
three M.S. graduatestudentsat UW-StevensPoint working on various aspectsof the
project. Detailedresultsof this projectare foundin the M.S. thesesof Peter
Arntsen,SteveHenkle,andWilliam VanRyswyk.In addition,muchof a PhD thesis
by Erik Harmson, UW-Madison containsinformation relative to the project. Fred
Madison, UW-Madison assistedwith severalaspectsof the project. Chris Mechenich
of the Central Wisconsin GroundwaterCenter compiled the survey of homeowner
practicesandattitudes,this datais summarized
in a reportby Mechenichet. at.
1991.
Two subdivisionsnear StevensPoint were selectedfor detailed analysisin this
study (Figure 1). The subdivisionswere selectedbasedon historical data indicating
groundwaterquality problems or the potential for groundwaterquality problems.
1
Primary objectivesof this project were as follows:
1.
2.
3.
4.
5.
6.
7.
Determine homeownerpracticesthat could impact groundwaterquality and
determineattitudesof homeownersrelative to groundwaterquality and
protection;
Determine nitrate-N loading to groundwaterfrom subdivisionsand evaluatethe
use of BURBS nitrogen massbalancemodel for predicting nitrogen impact;
Determine nitrogen contribution from septic systemsand lawns;
Determine the impact of individual septic systemson nitrate-Nand
phosphorousconcentrationsin groundwaterdowngradientof the system;
Determine if volatile organic chemicals(VOCs) are reaching groundwater
from subdivisionactivities;
Evaluatethe various monitoring systemsthat could be usedto determine
subdivisionimpacts on groundwater;
Evaluatethe use of geophysicaltechniquesfor locating septic systemeffluent
plumes.
Figure 1. Upgradient land usesand locationsof the subdivisionstudy sitesin
PortageCounty, Wisconsin.
?
B. Literature Review
The following is a review of literature relevant to the movementand fate of
potential groundwatercontaminantsfrom an unseweredresidential subdivision in the
Central Wisconsin SandPlain. Specific sectionswill be devotedto SandPlain
Geology, Subdivisionsand Nitrates, Septic Systems,Lawns, and PreviousWork in
the Study Area.
Sand Plain Geology
The geology of the Central Wisconsin SandPlain is characterizedby a
relatively thick layer of highly permeableglacial sedimentsoverlying impermeable
rock (Faustini, 1985). The glacial material consistsprimarily of outwash sandsand
gravels and tendsto be quite uniform in compositionboth laterally and vertically
(Weekset aI., 1965). Though the sandplain is often assumedto be homogeneous,
inconsistencies,such as layers or bandsof higher or lower hydraulic conductivities,
have been noted (Manser, 1983, Kimball, 1983, Stoertz, 1985).
Reportedhydraulic conductivitiesin the sandplain range from 0.05 cm/sec
(130 ftlday) (Weeks, 1969) to 0.18 cm/sec (500 ft/day) (Weeksand Stangland,1971),
with Faustini (1985) reporting an averagefrom severalsourcesof 0.10 cm/sec (270
ft/day). Slug testsperformed in the study areasby Harmsen(1989) indicated slightly
lower values of hydraulic conductivitiesranging from 0.02 cm/sec to 0.07 cm/sec (57
ft/day to 198 ft/day).
Harmsen (1989) reported a range of 96.5 to 99.7 percent sandfrom samples
takenin the upper15 metersin the studyareas. It wasalsonotedthat the sands
graded to coarsesandsand gravels at 23 to 25 metersbelow the surface.
3
Thicknessesof unconsolidatedsedimentsoverlying bedrock in the region
ranging from 0 to 27 meters (0 to 90 ft. were reported by Holt (1965) and by Weeks
et at. (1965)duringan investigationof the Little PloverRiver Basin. Harmsen
(1989) reported an averagedepth to bedrock of 33 meters(108 ft.) in the Jordan
Acres subdivision and an averagedepth to bedrock of 30 meters(98 ft. in the Village
Green subdivision. Thesevalues are estimatestaken from well logs in the region of
the subdivisions.
Effective porosities reported by Weekset al. (1965) in the Little Plover River
Basin ranged from 27.7 to 35.7 percent, with an averageof 32.3 percent. Stoertz
1985) reported a range of 36.5 to 40.5 percent in five repackedsamplestaken from a
site near Wisconsin Rapids.
Using an estimatedaverageeffective porosity of 0.23 and measuredhydraulic
gradientsof 0.0025 and 0.0020 for the JordanAcres and Village Green subdivisions
respectively,Harmsen (1989) calculatedaveragehorizontal seepagevelocities of 0.45
m/day (1.48 ft. in JordanAcresand0.30 m/day(0.98 ft.) in Village Green.
Subdivisions and Nitrate-N
Studiesevaluatingthe impact of rural housingon groundwaterquality have
been limited. The studiesthat have beenconductedhave focusedprimarily on the
loading of nitrate-N from septic systemsand to somedegreelawns.
Nitrate-N is of specialconcernas a groundwatercontaminantbecauseit has
beenassociatedwith methemoglobinemia(blue baby syndrome). Methemoglobinemia
most often occurs in infants as a result of the ingestion of high nitrate-N water. The
nitrate-N is convertedto nitrite in the digestive systemand then reactswith the
4
hemoglobinin the blood converting it to methemoglobin(Mechenich, 1988). The
methemoglobincannotcarry oxygen to the body as the normal hemoglobincan,
resulting in oxygen deprivation (indicatedby bluish-gray skin color) and possibly
resulting in death. As an infant agesthe pH in the stomachdecreasesand the
susceptibility to the diseasealso seemsto decrease(Mechenich, 1988). The Stateand
Federal Standardfor nitrates in drinking water is 10 fig/I.
Studieshave suggested
that concentrationsof nitrate-N as low as 13 mg/l can causemethemoglobinemia
(Vige1et al., 1965).
Nitrate-N has also been associatedwith the potential for the formation of
nitrosaminesin soil (Brown et aI., 1980), and in the human digestive system
(Mechenich, 1988). Nitrosaminesare amongthe most potent and broadly acting
carcinogensknown (Harmsen, 1989).
Numerous studiesemploying groundwatermonitoring and modeling have
demonstrateda correlation betweengroundwatercontaminationand onsite sewage
disposaldensity (Bicki and Brown, 1991). The density of septic systemsin an area is
usually regulatedby stateor local agenciesthrough zoning ordinancesspecifying
setbackdistances. Septic systemsetbackdistancesare specifiedminimum distancesa
septic tank or drainfield must be from surroundinghomes,property lines, or water
supply wells and often indirectly dictate the minimum lot size possible. As a result,
lot size is often basedupon engineeringrather then environmentalconsiderations
(Perkins, 1984). According to the EnvironmentalProtection Agency (1977), in most
parts of the country septic tank density is the most important factor influencing local
arid regional groundwatercontamination. Perkins (1984) interpreted this to indicate
5
that drinking water well setbackdistancesdo not appearto be adequatein many
regions to prevent groundwatercontaminationfrom septic systemeffluent.
Perkins (1984) reviewed severalstudiesand empirical modelsdesignedto
estimatethe minimum lot size necessaryto prevent groundwatercontamination.
Estimatedlot sizesranged from 0.2 to 0.4 hectares(0.5 to 1.0 acres)basedon
reported data and 0.3 to 0.4 hectares(0.75 to 1.0 acres)basedupon theory. Bicki
and Brown (1991) reviewed literature relative to septic systemdensitiesand reported
that lot sizesin this range (0.2 to 0.4 hectares)are often cited as minimums for the
prevention of groundwatercontaminationfrom septic systemeffluent. They also
noted that somestudieshave found groundwatercontaminationfrom nitrate-N with lot
sizesin this range due to site specific soil, hydrogeologic,and climatic conditions.
Baumanand Schafer(1984) presenta simplified model and examinethe
possiblegroundwaterquality impacts of nitrate-N loading from septic systemsand the
factors influencing such impacts, They also proposethe addition of hydrogeologicor
aquifer assessmentcriteria to the septic systemsite evaluationprocedure. Included in
this aquifer assessmentcriteria would be considerations for depth to aquifer, aquifer
thickness,rechargerates, and groundwaterflow velocities.
Depth to aquifer is important in .the evaluation of the potential for
denitrification to occur. Baumanand Schafer(1984) specify that in this evaluationof
the vadosezone, specific characteristicsto look for are; 1) the presenceof restricting
layers which may create anaerobic conditions, 2) temperature (warmer temperatures
associated with shallow water tables promote metabolic activity, thereby enhancing
denitrification), 3) residencetime in the vadosezone {longer periods allow more time
6
for denitrification to occur if reducing conditionsexist) and 4) Dissolved organic
carbon (DOC) contentof the groundwater(higher concentrationsstimulatebacterial
activity, increasingthe potential for both anaerobicconditions and denitrification).
Groundwaterflow velocities becomeimportant when evaluatingthe dilution
potential of an aquifer. Dilution is often the final processrelied upon to reduce
concentrationsof conservativesolutesto an acceptablelevel once they enter a
groundwatersystem. Walker et al. (1973. II) concludesthat 0.2 Ha is neededas a
minimum lot size necessaryto reducegroundwaternitrate-N concentrationto less then
10 mg/l downgradientof on-site disposalsystemsin sandyWisconsin soils, by stating
that" dilution is an unacceptablepart of the wastetreatmentsystembecauseflow
patterns are often difficult to predict" . Walker et al. (1973, II) discussa preferable
conceptto relying upon dilution as the final treatmentprocess. This conceptwould
be to consider the water table as the lower boundary of the treatmentsystem,thereby
requiring purification of the wastesin the unsaturatedzone beneaththe seepagebed.
Admittedly, this conceptseemsmuch more "holistic" in theory but in certain soils,
such as those found in the sandplain, achievingcompletepurification with a
conventionalseptic systemis unlikely. Pitt et al. (1975) reported that in some
aquifers with high groundwaterflow velocities (often associatedwith sandand gravel
aquifers) the dilution potential can be significant. In a sensitivity analysisperformed
on the model formulated by Baumanand Schafer(1984), flow velocity was
establishedas a model sensitivevariable. The model indicated that in lower velocity
flow systemsthe effects of dilution are minimal and are therefore more susceptibleto
appreciable contamination,
7
Sandand gravel aquifers are often associatedwith high flow velocities,
Robertsonet at. (1991) reports that recent studiesindicate that the dispersive
capabilities, and therefore the contaminantdilution potential, of many sandand gravel
aquifers are much less then previously thought. The study conductedby Robertsonet
al. (1991) in Canadafound low transversedispersionin a shallow unconfinedsand
aquifer downgradientof two small septic systems. The report cites severalrecent
natural gradient tracer experimentsin sandsalso measuringlow dispersionvalues (ie.
longitudinal dispersivity = 1 ffi, vertical transverse dispersivity = 0.004ffi, and
horizontal transversedispersivity = 0.01 m) as reportedby (Sudickyet al., 1983;
Freyburg,1986; Garabedian,1987; Moltyaner and Killey, 1988 a and b; all cited by
Robertsonet at. 1991). Robertsonet at. concludethat the minimum well-septic
systemsetbackdistancescommon throughoutNorth America should not be expected
to protect well-water quality in situationswhere mobile contaminantssuch as nitrate-N
are not attenuatedby chemical or microbiological processes.
Another important considerationin the evaluationof the impact subdivisions
may have on groundwateris the effective depth of mixing occurring beneaththe
subdivision The sensitivity analysisperformed by Baumanand Schafer(1984) on
their model indicated that in low velocity flow systems,the effective depth of mixing
had little impact on nitrate-N concentration,and had only minimal effect on nitrate-N
concentrationin a higher velocity flow systeni Harmsen(1989) comparesvaluesof
averageflow velocity in the sandplain, 0.3 to 0.6 m/day (1-2 ft/day) (Rothchild,
1982), and an averagelot size of less than 0.4 hectare(typical of those found in the
study area) to the results presentedby Baumanand Schafer(1984) and concludesthat
8
mixing depth is likely a model sensitiveparameterin the study area.
Data pertaining to the depth of mixing occurring under subdivisionsis notably
absent. Wehrmann (1983) statesthat groundwaterbeneathunseweredsubdivisions
possessinga large number of wells "will be mixed quite effectively". But as noted by
Harmsen (1989), no studiessupportingor contradicting this theory could be found.
Baumanand Schafer(1984) also evaluatethe sensitivity of their model to
backgroundnitrate-N concentrationsof incoming water and found that it had little
impact on the analysis. Incoming concentrationsranging from
to 7 mg/! nitrate-N
had very little effect on nitrate-N concentrationsin a simulatedsubdivisionwith
varying lot sizes. Backgroundnitrate-N concentrationslike thosecommonin the
Village Green subdivision (> 20 mg/l) reported by Harmsen(1989) would likely have
made more dramatic an impact on their analysis.
Tinker (1991) evaluatedgroundwaterfrom five subdivisionsin West Central
Wisconsin using private water supply wells. Resultsindicate that nitrogen from septic
systemsand lawn fertilizer causenitrate-N concentrationsto increasein groundwater
beneaththe downgradientside of the subdivisions. Three of the five subdivisionshad
nitrate-N levels exceedingthe drinking water standardof 10 mg/!. Tinker (1991) also
evaluatesthree nitrogen massbalancemodelsin an attempt to identify the possible
sourcesof nitrate-N in the subdivisionwells.
In a comparisonof nitrogen in shallow groundwaterfrom seweredand
unseweredareasof Long Island, New York, researchersfound no significant
difference existing betweenmediannitrate-N concentrationsin groundwatersamples
from each area (Katz et al., 1980). The authorsacknowledgethat the lack of
9
significant difference betweenthe two may have been due to samplingbias, landfills
and agricultural sources,and/or residual contaminationfrom before the area was
sewered. The study did find significantly lower nitrate-N concentrationsin wells,
screenednear the watertablebeneaththe seweredarea. The results indicated that the
nitrate-N concentrationswere being reducedby sewering,but that the dilution process
was quite slow in the Long Island aquifer.
A more conclusive study conductedin an 80 squarekilometer (30 squaremile)
denselypopulated, unseweredarea in East Portland, Oregon showeda significantly
higher concentrationof nitrate-N in groundwatersampleswhen comparedto samples
taken from surroundingseweredareas(Quan et al., 1974).
A computerprogram developedby Cornell University and known as the
BURBS model (Hughesand Pacenka,1985)was usedby Leonard (1986) in
Wisconsin to determinethe minimum lot size necessaryto prevent nitrate-N
concentrationsfrom exceeding10 mg/i. The model utilizes inputs from septic
systemsandfertilizersandperformsa detailednitrogenmassbalance.Leonard's
analysiswas performed on two soil types commonto Wisconsin, Plainfield Sandand
Grays Silt Loam. Resultsindicated that a minimum lot size of 0.8 Ha was necessary
to achievethe 10 mg/l nitrate-N concentration. Soil type was found to have little
effect on the nitrate-N concentrationof groundwater. Nitrate-N concentrationwas
found to increasewith housing density but at a decreasingrate. The BURBS model
estimatesnitrate-N concentrationsin rechargewater as it doesn't accountfor
backgrounddilution from groundwaterpassingunder the site.
Anderson et al.(1987) developeda contaminanttransport model to assistin
10
selectingactual subdivisionsfor field groundwatermonitoring. Models for the mean
values of input parametersand for uncertainvaluesof the input parameterswere
developedand solutionsobtainedfor typical Florida groundwaterconditions. The
model was determinedto be a "useful tool" in assessingthe potential impact of
subdivisionson groundwaterquality which would likely take many years to realize in
a field monitoring study.
Septic Systemsand Groundwater Quality
Septic tanks contribute more than I trillion gallons of wastewaterto the
subsurfaceevery year (OTA, 1984). This waste originatesfrom over 22 million
septic tanks in the U.S., The above statisticsmake septic tank systemsthe leading
contributor of wastewaterto the subsurfaceand the most frequently reported causeof
groundwatercontamination(U.S. EPA, 1977)
With statisticslike these,one would expectthat researchin the area of septic
systemperformanceand effectiveness,and the impacts of septic systemson
groundwaterqualitywould be commonandon-going. Althoughtherehasbeena
good deal of researchevaluatingthe impact of conventionalsystemson groundwater
quality, the use of thesesystemsstill dominatesin many areaseven where proven
ineffective.
Cogger (1988) identified three primary parts of a septic system: the septic
tank, the absorptionarea, and the surroundingsoil. Wastesenter the septic tank via a
gravity feed sewer line from the household. Typically no separationof gray water
(water used for laundry, bathing, etc.) from blackwater (toilet wastes)is made. Once
in the tank, the heavier materialsand solids will sink to the bottom of the tank where
11
decompositionwill occur, thus reducing the quantity of organic material (Reneauet
aI., 1989). At the effluent surface,in a properly functioning tank, a scum layer of
floating material containing greasesand fats will form. Decompositionwill also
occur here.
Water levels in the tank are controlled by an inlet and an outlet located at
oppositeends of the upper portion of the tank and separatedby baffles. The baffles
are designedto prevent the surfacescum layer and bottom sludgematerial from
escaping. In a properly functioning system,only a semi-clarified effluent from the
center of the tank is allowed to dischargeto the soil absorptionsystem(Cantor and
Knox, 1985).
Reneauet at. (1989) reported anaerobicdigestion in the septic tank results in a
reduction of sludgevolume by 40%, biological oxygen demand(BOD) by 60%,
suspended solids by 70 %, and conversion of much of the organic-nitrogen to the
ammonium form (NH4 +).
The clarified effluent entering the absorption area will eventually cause a build
up of what is termed a "biological mat" at the interface of the absorption field and the
surroundingsoil (CantorandKnox, 1985). The development
of a biologicalmatcan
play an important role in effluent treatment,particularly in soils with high hydraulic
conductivities. This mat, sometimescalled the crust layer, is a result of clogging of
soil pores with organic materialsand biological growth (Brown et al., 1980; Laak et
at. 1975). In permeablesoils the mat servesas an effective degradativefilter to
suspended and dissolved organic matter and tends to enhance treatment by lengthening
travel times and increasingtortuosity (Brown et al., 1980; Reneauet al., 1989).
12
Walker et al., (1973 I) noted that below the mat, which remainsanaerobicand
saturatedmost of the time, aerobic conditionsoften exist.
A problem often associatedwith the use of conventionalseptic systemsin
highly permeable soils is uneven distribution of effluent out of the distribution pipes.
This phenomenonresults in elevatedloading rates to a relatively small portion of the
absorptionarea (Reneauet al., 1989) It occurs when the vast majority of effluent
entering the distribution pipe discharges in one area due to the permeability of the
soils below, Cogger (1988) discussesthis phenomenonand notes that new systemsin
coarsesoils may be susceptibleto localized overloadingresulting in poor treatment.
Due to the elevatedloading rates in specific areas,the potential for
groundwater contamination increases because saturated conditions prevail.
Associated
with these saturated conditions is an accelerated formation of the biological mat,
which will then act to decreaseinfiltration at that location (Reneauet al., 1989). This
preferential discharge usually occurs at the beginning of a distribution trench (where
the effluent first encounters perforations in the distribution pipe), As the biological
mat builds up in that area the discharge will be displaced further and further down
along the length of the pipe, This phenomenonis well documentedand is referred to
as "creepingfailure" (USEPA,1980), (Reneauet aI., 1989),
Nitrogen
Many potential chemical contaminantsexist in septic tank effluent but nitrogen
is often thought to representthe most seriousthreat to humanhealth. Nitrogen in the
form of nitrate-N representsthe greatestthreat becauseof its associationwith
methemoglobinemiain infants and becauseit is very soluble and chemically inactive
13
in aerobic environments,often resulting in virtual unrestrictedmobility in soil and
groundwater(Reneauet aI., 1989). This mobility and the fact that many land use
activities are often associatedwith the formation or application of nitrates are the
principle reasonsnitrate-N is of such concern.
The fate of nitrogen in the environmentis complex. It results from a variety
of physical, chemical, and biological mechanismswhich in turn are greatly influenced
by environmentalconditions (Brown et aI., 1980).
Septic tank effluent typically averages40-80 mg NIl, of which 75 percent is
soluble ammoniumand 25 percent organic-N (Walker et al., 1973,11;Brown et al
1980; Reneauet aI., 1989). Brown et aI. (1980) goeson to statethat the vast
majority of the organic-N is "sorbed and transfonned" to ammoniumin the anaerobic
crusted zone or mat of the absorptionfield
Nitrogen leaving the anaerobicbiological mat zone as ammoniumand entering
the soil profile is often oxidized to nitrate-N. This largely biological process,shown
below, is known as nitrification (Brown et aI., 1980).
NH.
+
+
Nitrosococcus
Nitrosomonas > NOz'+ HzO+ 2H+
202
Nitrobactor
>
N02- + 1/202
N03"
In a properly functioning absorptionsystemmost of the nitrogen will be
convertedto nitrate-N in the first few inchesof the aerobic soil surroundingthe
absorptiontrench (Dudley & Stephenson,1973; Walker et al., 1973). Oxygen
diffusion into the soil zone is the most rate limiting factor determining the form of
14
nitrogen present (Reneauet al., 1989). Environmentalconditions such as moisture
content below the mat can indirectly control the processby restricting soil oxygen or
in extremely dry conditions may result in a reduction of bacterial populationsand thus
limit nitrification (Brown et aI., 1980).
In an evaluationof the potential for nitrification to occur in the sandy
inorganic soils of the New JerseyPine Barrens, Brown at. at. (1980) noted that the
low pH and base statusof the native soils may discourageoxidation of ammonium,
but then commentedthat the near neutral wastewaterwould probably increasesoil pH
to an acceptablerange overtime. Although this may be the case,once nitrification
beganto occur there would likely be a subsequentdecreasein pH as noted by Reneau
et at. (1989) and Alhajjar et at. (1990) and discussedbelow.
Brown et al. (1980) also report that cooler temperaturesassociatedwith the
northeastern regions of the United States may inhibit the activity of nitrifying bacteria
resulting in the movementof ammoniumto groundwater. However, other
investigators(Viraraghavanand Warncock, 1976; Viraraghaven, 1985) found that
winter conditions posedno threat to septic systemoperationand cited studiesin
Alaska where septic systemsperformed satisfactorily.
The primary mechanismfor removal of nitrogen from soils is denitrification.
Denitrification is the reduction of nitrates to gaseousnitrogen by bacteria under
anaerobicconditions in the soil (Cogger, 1988). This reaction is depictedin the
following equation, where CHzO representsorganic matter as a carbon source
(Robertsonet aI., 1991),
4/sNO3-
+ CH2O
>
z/sNz
+ HCO3-+ l/sH+ + z/sHzO
15
A properly functioning septic systemin sandywell aeratedsoils (such as those
found in the study areas)will have minimal denitrification, and then only in anaerobic
microsites (Bouma, 1979; Reneauet al., 1989).
A study conductedby Alhajjar et al. (1989) in Wisconsinevaluatedthe impact
of phosphatebuilt versus carbonate-builtlaundry detergentson groundwaterquality
downgradientof septic systems. The authorsconcludedthat the use of phosphatebuilt laundry detergentsimproved the efficiency of nitrogen removal during effluent
percolation through septic systemdrainfields and reducedthe nitrate-N level in
downgradient groundwaterplumes without any significant effect on phosphorus
concentrations. They theorize that the greater amountsof phosphorusreaching the
soil from the phosphate-builtdetergentsstimulated"prolific growth" of denitrifying
bacteria in the clogging mat and soil, thus enhancingthe removal of nitrogen.
Cogger and Carlile (1984) provided indirect evidenceof denitrification around
septic systemsbut found that it varied from one systemto another, seasonally,and
was most effective in wet soils which were otherwiseunsatisfactoryfor wastewater
treatment.
Denitrification may be significant in soils with restricted drainagebut
nitrification of ammoniummust occur first, then denitrifying bacteriaand a carbon
sourcemust also be present. Robertson,et aI. (1991), in a study conductedin
Canada,reported nitrate-N concentrationsdecreasingfrom 20 mg/l to less than 0.5
mg/l in the last meter of flow before discharginginto the Muskoka River. The
nitrate-N had traveled 20 metersfrom a septic systembefore "vigorous denitrification
16
occurred in the riverbed sedimentsas a result of anaerobic conditions existing there",
Carbon was also abundantin thesesediments.
Acidity producedfrom the nitrification of ammoniumresulted in depressedpH
levels in the plumes of both systemsstudiedby Robertsonand has been noted by
other investigators. A study conductedin Australia (Whelan, 1988) measureda
significant reduction in pH (9.0 to 5.5) causedby the nitrification processbelow a
soak well. Reneauet at. (1990) point out that the lowering of pH to this level could
adverselyaffect the activity of denitrifying bacteria. Alhajjar et aI. (1990) also noted
a substantialreduction in the pH of groundwaterimpactedby septic leachate.
Thesedata indicate that well drained soils, traditionally consideredto be
ideally suited for conventionalseptic systems,are very susceptibleto groundwater
contaminationfrom nitrates due to the limited potential for denitrification. The most
probable mechanismfor the reduction of nitrates under theseconditions is dilution by
groundwater(Reneau,et at, 1989). Table 1 summarizessomerelevant data from
septic systemstudies.
17
Reference
System Emuent
Age
Nitrogen
(yrs)
(mg/l)
Groundwater
Nitrate-N
(mg/l)
Ellis & Childs ..
15
8.0
Ellis & Childs"
8
Dudley & Stephenson"
~
27.1-33.8
Dudley & Stephenson"
8
Dudley & Stephenson"
9
Depth to
Groundwater
(m)
Distance
Moved
(m)
1.5-1.8
100
0.9-1.2
9
15.5
3-4
6.1
27.1-33.8
2.4-20.3
4
9.1
27.1-33.8
13.8
17.J
0
27.1-33.8
2.4-11.4
7.5
0.9
Walker et al. 1973"
40
5-6
0
Walker et al. 1973"
10
5-6
70
Walker et al. 1973"
12
Dudley & Stephenson"
35
Shaw and Turyk
5-10
46-105
15-101
3-7
5-13
Virarghaven & Wamcock 1976
New
77-111"""
0.4
2-3
12
Rea & Upchurch (1980)
50
10
1
25
Robertson et al. 1991
12
30..
33"""
2.5
0
CQ..
~Q
...
...
As cited by Brown and Associates, 198O, p.51
Reported value of ammonia nitrogen in septic tank effluent
Reported background nitrate-N of 27 mg/l
Table 1. Summary of field studies of nitrate-N movement from septic systemsin
groundwater.
Phosphorus
Literature relative to phosphorusmovementaway from septic systemsis less
consistentthen that of nitrogen. Soils appearto vary greatly in their ability to adsorb
soluble phosphateions (Brown et al., 1980) The greatestenvironmentalconcern
associatedwith phosphorusmovementaway from septic systemsis the eutrophication
of surfacewater bodies (Cogger, 1988). Phosphorusis often the limiting nutrient in
aquatic ecosystems. Excessiveadditionscan causenuisancealgaeblooms and
enhancedgrowth of aquatic macrophytes,often resulting in oxygen depletion.
Phosphorusin septic tank effluent originatesprimarily from human wastesand
19
detergents(Brown et al., 1980). The contribution from the latter has likely decreased
in Wisconsin in recent years since the use of phosphatebasedlaundry detergentshas
been restricted. However, phosphatesare still a componentof many non-laundry
householddetergentsand cleaners(Shaw, 1988). Phosphatemovementthrough most
soils is limited, and seemsto be controlled primarily by adsorptionand precipitation
type reactions(Reneauet aI., 1989).
Phosphateprecipitation in the soil is primarily dependantupon the pH of the
soil andthe presenceof aluminum,iron, calcium,andorganiccolloids(Laaket al.,
1975). Laak et al. (1975) also report that phosphorusfixation is at a minimum at
near neutral pH and tendsto be at a maximum at pH extremes. In soils where iron
and aluminum are present(usually associatedwith lower pH's) phosphatescan be
chemically adsorbedby hydrous oxides of aluminum and iron forming an extremely
insoluble gel complex (Kuo and Mikkelsen, 1979). In calcareoussandy soils such as
those found in the study area, precipitation reactionswith compoundscontaining
phosphorusand calcium would likely dominate(Reneauet al., 1989) although iron
and aluminum precipitation and/or sorption may also occur.
Childs et al., (1974) evaluatedeffluent migration away from several septic
systemssurroundingHoughton Lake, Michigan. The study reported phosphorus
mobility equivalentto that of nitrates and chlorides in some situationswhile at other
nearby sites very little phosphorusmovementwas noted. The difference in
phosphorusmobility from site to site was attributed to variations in adsorptive
capacity betweensoil types and loading rate variations.
Nagpal (1986) reported that phosphorussorption is more affected by an
19
increasein hydraulic loading then by phosphorusconcentrationin the effluent.
Nagpal (1986) also suggeststhat measuresto control hydraulic loading at anyone
time would be more effective at reducing phosphorusmovementthrough the soil then
controlling soil type or phosphorusconcentrationin the effluent. Lance (1977) also
reported that phosphorusremoval from effluent was proportional to loading rates.
Reneau(1978; as cited by Reneauet al., 1989) suggestedthat a low pressuredosing
systemwould greatly reducephosphorusmovementin somesituationsby achieving
uniform effluent distribution and allowing the systemto be placed at a shallower
depth, thus maximizing the unsaturatedzone.
In a recent Canadianstudy, Robertsonet al. (1991) evaluatedphosphorus
movementin sandyaquifers from two septic systems. Although phosphorus
concentrationsin the tile effluent of about 10 mg/l PO4-Pwere reported at both sites,
significant subsurfaceattenuationwas noted. At one site no detectablePO4-Pwas
observedin the groundwater,and the other site indicatedvery little attenuationin the
unsaturatedzone, while significant attenuation(> 5 mg/l to < 0.02 mg/l) occurred
after several metersof flow in the saturatedzone. The authorsattribute the phosphate
removal in the unsaturatedzone at the first site (pH = 5.1, systemage4 yrs.) to
sorption or precipitation with iron or aluminum. Phosphateattenuationat the second
site (pH
7.0, systemage 14 yrs.) was believed to be controlled by precipitation
in the saturatedzone (Robertson
with Ca+2 to form hydroxylapatite(Ca1O(PO4)6(OH)2)
etal.,1991).
A field investigationof the efficiency of a septic systemon a relatively fine
textured soil (sandyloam and silty loam), conductedby Viraraghavenand Warncock
?O
1976), reported concentrationsof phosphate-Pin the groundwaterof 5 mg/l to 10
mg/l approximately 15 meters(50 feet) from the tile bed. The authors noted that the
phosphatereduction achievedin the study was low but offered no explanationas to
why. The drain tile wasa newadditionto an existingsystemso the attenuation
capacityof the soil shouldnot havebeenexhausted
from previousloading. Near
ground level water tableswere noted during the spring snow melt at the study site.
Cogger (1988), in a review of literature relative to septic systemsand
groundwatercontamination,points out that phosphatemovementis usually associated
with soils having limited fixation capacitiesand is especiallyprevalent around old or
heavily loaded systemswith shallow water tables. This is consistentwith the results
of a soil column study conductedby Sawhney(1977). The study concludedthat soils
have a finite ability to removephosphorusif continuouslydosed. Once phosphorus
breakthroughoccurred, increasinglylarger amountsof phosphorusappearedin the
column effluent. Consequently,after prolonged use of a soil, especiallya soil of low
sorption capacity, subsurfacewaters could be expectedto contain high concentrations
of phosphorus.
Numerousinvestigatorshave documentedthat phosphorusmovesrather freely
once it enters the saturatedzone (Childs et al. 1974; Viraraghavenand Warncock,
1976; Reneau, 1979). Other studies have indicated that significant attenuation can
occur in the saturatedzone (Robertsonet aI., 1991), Table 2 summarizessome
relevant data from septic systemstudies. The mechanisms controlling phosphorus
movement will be greatly influenced by loading rates and the geochemical conditions
21
Reference
System
Age
(yrs)
Ellis & Childs, 1973
.
P04 in
Effluent
(m~/l)
15
PO4 in
Groundwater
(mg/l)
Depth to
Groundwater
(m)
Distance
Moved
(m)
0.099
1.5-1.8
100
11.6
0.9-1.2
9
Ellis & Childs, 1973 .
8
Childs et al. 1973
10
upto8
shallow
16
Childs et 81. 1973
10
up to 8
shallow
30
Dudley & Stephenson1973*
5
0.05
3-4
6.1
Dudley & Stephenson1973.
8
0.65
4
Dudley & Stephenson1973.
9
up to 5.5
17
12.2
13.16
0.05-0.28
7.5
18
6.25-30.00
upto5
2-3
12
10.8
0.01-0.55
10.4
up to 5
8
Dudley & Stephenson 1973+
Viraraghavan & Warncock
new
Reneau1977"
11.5
27.1-33.8
Rea & Upchurch 1980
50
Robertson et al. 1991
12
8
4
2
0
Robertson et al. J99\
1-2
13
0.01
3
0
'"
As cited by Brown and Associates,1980, p.51
Table 2. Summary of field studies of phosphate movement from septic systemsin
groundwater.
existing in the unsaturatedand the saturatedzone. Phosphorusmovementin the
coarsesoils of the study areasis likely, especiallywhere heavy loading and poor
effluent distribution is occurring or in old systems.
Bacteria
Bacteriological contaminationof groundwaterfrom septic systemsis well
documentedbut is not a focus of this.project. For a comprehensivediscussionof
bacteriologicaland viral contaminationof groundwaterfrom septic systemsrefer to
YatesandYates,1989;Yates,1985;andReneauet aI., 1989.
Chlorides and Other Potential Contaminants
Chlorideis a naturallyoccurringanionin surfaceandgroundwaters,whichis
usually presentat low concentrations. It is also a commonconstituentin animal and
22
humanwastes,andoftena component
of roadde-icingagents. As a result,elevated
concentrationsof chlorides are often indicative of contaminationfrom man-made
sources.Concentrationsof chloride in septiceffluent vary with human diet and with
the quality of the water supply source(Alhajjar et al., 1990). Septic systemsdo not
effectively remove chloride due to it's anionic form and conservativenature, As a
result, it is often usedas an indicator of contamination'(A1hajjaret at. , 1990)
Alhajjar et al., (1990) statistically evaluatedthe use of four groundwater
chemical characteristicsto determinewhich were best suited as indicators of
groundwatercontaminationfrom septic systems. Resultsindicated that of the four
chemical characteristicsevaluated(CI-, electrical conductivity, pH, and fluorescence)
only chloride was considered a conservative tracer, and thus the best indicator.
Electrical conductivity and pH were classifiedas semi-conservativeand were only
"acceptable" as indicators, Fluorescence,originating primarily from optical
brighteners in laundry detergents, was considered a poor indicator of septic
contaminated groundwater. The authorsgo on to statethat" septic systemsare not
sourcesoffluorescence to groundwater, andfluorescenceis not a reliable indicator of
organic
pollutants in groundwaterin the vicinity of septic systems"(Alhajjar et at
1990) However, results of this study do not supportthis conclusion
Lawn Studies
Since 1970, pesticideand fertilizer use on private home lawns has steadily
increased(Watshke, 1983 as cited by Morton et aI., 1988). With this increased
chemical usagehas come increasedthreatsto surfaceand groundwaterresources. Inground home lawn irrigation systemsare also becomingmore common, especiallyin
23
areaswith well drained soils such as the Central Wisconsin SandPlain. Home lawn
irrigation water is often applied with little regard for the moisture statusor water
holding capacity of'the soil, which often results in over-watering(Morton et al.,
1988). Irrigation resulting in over-wateringhas been shown to significantly increase
nitrate-N leaching (Endelmanet aI., 1974; Rieke and Ellis, 1974).
Petrovic (1990) reviews current literature on the fate of nitrogenousfertilizers
applied to turf grass. The report concludesthat the leaching of fertilizer nitrogen
applied to turf grassis dependantupon soil texture, type and amount of nitrogen
applied, timing, and irrigation/precipitation events. Suggestedpracticesfor
minimizing the impact of nitrogen to groundwaterinclude using irrigation water only
to replace the amount of water usedby plants, using slow releasenitrogen sources,
and avoiding fertilization and irrigation on sandysoils (Petrovic, 1990).
In a sandand gravel aquifer on Long Island, New York, Flipse et at. (1984)
evaluatednitrate-N concentrationsin groundwaterbeneatha seweredsubdivision
The analysisindicated a significant regional increasein nitrate-N concentrations(0.22
mg/1/yr) over a sevenyear period. The principle sourceof this nitrate-N was
attributed to fertilizers from lawns.
Gold et al., (1990) comparednitrate-N lossesto groundwaterfrom agricultural
and suburbanland uses. U sing ceramic suction lysimeters, the study comparedsoil
water percolate from the following land uses;
1) Urea-fertilized silage corn with a rye cover crop.
2) Urea-fertilized silagecorn with no cover crop.
3) Manure-fertilized silage corn with a rye cover crop.
4) Fertilized home lawn.
5) Unfertilized home lawn.
24
6) Mature, mixed oak-pineforest.
7) Conventionalseptic systemfrom a three person home.
8) Forestedarea.
All treatmentswere located on well drained, silty or sandyloam soils over highly
permeable,stratified drift depositsof sandsand gravels.
The septic systemachievedan estimateddissolvedinorganic nitrogen (DIN)
removal of 21 percent in the septic tank and absorptionarea. This percentagewas
basedon a measurednitrogen loading rate of 9.5 kg/yr (21Ibs./yr) in drainfield
percolatecomparedwith the U.S. EnvironmentalProtection Agency (1980) estimated
averageof 12 kg/yr (26.4 Ibs/yr) for a three personhome.
The urea fertilized home lawn treatmentreceivedas much nitrogen as the urea
fertilized silage com (200-250kg/ha/yr) but resultedin much lower nitrate-N
percolate. Most of the nitrate-N flux observedin the lawn plot occurred during the
spring thaw (Gold et al., 1990)
The urea fertilizer was applied to the lawn in small incrementsthroughout the
growing season. This seemedto minimize leachingof nitrogen from the root zone.
However, the authors note that substantialnitrogen leaching can be expectedfrom turf
grass when nitrate-N forms of fertilizer are applied and when over-watering occurs
citing Morton et aI., 1990and Rieke and Ellis, 1974.
Theseresearchersconcludethat replacingproduction agriculture with unseweredresidential subdivisionswill not markedly reducenitrate-N concentrationsin
groundwater (Gold et al., 1990).
Previous Studies in the Project Area
Harmsen (1989) evaluatedthe nitrate-N distribution occurring under both the
25
JordanAcresandVillage Greensubdivisions.Nitrate-Ndistributionswere
determinedvia two multilevel well transectsplacedparallel to groundwaterflow in
each subdivision.
At Jordan Acres the affect of the subdivisionson groundwaterquality was
apparent. Elevated nitrate-N concentrationsin downgradientwells were attributed to
septic systemsand lawn fertilizers.
The Village Green Subdivisionshowedless conclusively the impact attributable
to subdivisionactivities. Nitrate-N concentrationsincreasedwith depth at this
subdivision, and actually tendedto decreaseat the downgradientend of the
subdivision. The elevatedbackgroundconcentrationsof nitrate-N at.depth was
attributed to upgradientagricultural activities. The two subdivisionsrepresenttwo
extremecases,one with high, the other with low backgroundnitrate-N concentrations,
but neither are atypical of the sandplain region
Harmsen (1989) also noted that spatial nitrate-N distribution appearedto be
highly variable in the vertical and horizontal planes, and plumes originating in the
subdivisionswere vertically thin and someseemedto exhibit vertical bifurcation.
Sharp concentrationcontrastsmeasuredin the horizontal and vertical planes suggest
that mixing associatedwith hydrodynamicdispersionwas minimal (Harmsen, 1989).
Henkel (1992) evaluatedwater from monitoring wells downgradientof
individual septic systemswithin the subdivisionsfor organic compounds. Results
indicated that organic compoundsare presentin groundwaterin both subdivisions,but
in relatively small quantitiesas a result of homeownerproduct use and disposal
practices. Severaldetectsof VOC's wereconfirmed,but mostwereat very low
26
concentrations. The highestconcentrationof a VOC detectedwas 21.6 ppb of 1,1,1Trichloroethane(lll-TCA).
The statePreventativeAction Limit for Ill-TCA
is 40
ppb (Henkel, 1992).
Jonas(1990) conductedtoxicity testson groundwaterfrom subdivision
monitoring and private wells using Cerioda~hnia@hill. Three wells from the Jordan
Acres subdivision (1 monitoring, 2 private) and six wells from the Village Green
subdivision (2 monitoring, 4 private) were evaluated. Wells which displayedelevated
concentrationsof nitrate-N during previous testing were selected. Resultsindicated
that one private well from each subdivisionappearedto be toxic to Ceriodaphnia.
The author suggeststhat the results of thesetestsare probably more reflective of
inconsistentlaboratory procedures(feedingregimesand dilution water) then toxic
water quality problems, but offers no clear explanation.
27
C. Methods
Two subdivisionsin the StevensPoint area were selectedand instrumentedwith a
large number of monitoring wells during the period from 1987 to 1991 The selection
of the subdivisionswas basedupon local private well water quality information
obtainedfrom the EnvironmentalTask Force (ETF) at the University of WisconsinStevensPoint. Areas with differing upgradientland useswere selectedin an attempt
to 1) representsubdivisionstypical of the region, and 2) evaluatethe effects of
subdivision land use activities relative to upgradientland use activities in the same
groundwaterwatershed.
The following is a descriptionof the methods,techniquesand proceduresused in
the study.
Survey of Homeowners
.
During the spring of 1987, a survey was conductedof all householdsin both
subdivisions(seeAppendix C) to collect information relative to homeownerchemical
usage,waste disposalpatterns,and fertilizer/pesticide usage(Mechenich,et. aI.,
1991). The survey was conductedwith the assistanceof the Central Wisconsin
GroundwaterCenter. A personalinterview was also conductedwith many of the
respondents,at which time they were askedto sketchwell and drainfield locations in
their yards. Individuals interestedin having monitoring wells placed in their yards
were also identified at this time. Henkel (1992) summarizessomeof the results of
this survey.
The two subdivisionschosenfor the study are part of a larger researcheffort
evaluatingimpacts of unseweredsubdivisionson groundwaterquality, Namesof
28
property owners in thesesubdivisionswere obtainedfrom the PortageCounty Land
Recordsoffice. Vacant parcels were eliminated; only thoseactually living in the
subdivisionswere included. One hundredeighty-four (184) potential participants
were identified.
A two-part questionnairewas developedand is included as Appendix C The
first part, eight pagesfocusing on chemicaluse and disposalpractices, was mailed to
all subdivisionresidents. A cover letter explainedthe study objectives. Residents
were askedto completethe questionnaireand hold it for a personalvisit from
researchers.
Two weekslater, residentswere called to set up a personalinterview.
Researchersvisited eachhome and collectedand reviewed the first part of the
the secondpart of the survey,a three-page
questionnaire. They thenconducted
questionnairefocusing on attitudesand opinions about the causesand severity of
groundwatercontaminationand the acceptabilityof potential solutions. A water
samplewas also taken during the home visit and analyzedfor nitrate-N, chloride,
hardness,alkalinity, pH, specific conductance,and corrosivity index as part of the
larger researcheffort. Resultsof chemicalanalysesare included in Appendix A.
The residentsof 21 homesrefusedto participate, and another24 could not be
contactedduring the time frame of the study Participation rates were 89 percent in
the Jordan Acres subdivisionand 70 percentin the Village Green subdivision. In
total, 139 surveyswere conducted.
Data analysis was conductedusing the dBaseIII + data base software (AshtonTate Corporation, Torrence, CA) and SPSS-Xstatistical softwarepackage(SPSS,
29
Chicago, IL). Frequencieswere calculatedin quartiles for pesticideuse and
householdchemical use Chi-squareanalysis(CROSSTABS) and cluster analysis
(CLUSTER) procedureswere usedin SPSS-Xto searchfor significant relationships
betweenand among questionnaireparameters.
Monitoring Well Installation and Design
Four piezometers(survey wells) were installed around the perimeter of each
subdivisionduring the summerof 1987. The wells were constructedof 3.18 cm (Ill,
in.) PVC (polyvinyl chloride) and were fitted with 30.48 cm (1 ft.) slotted, 0.0254
cm (0.01 in.) slot size screens. The screenedintervals were positioned slightly
below the watertableto accountfor water level fluctuationswhile still reflecting near
watertableconditions. The wells were then surveyedwith respectto an arbitrary
datumof 30.48m. (100.00ft). Surveyingerrorswerelessthen0.006and0.012m.
for the Jordan Acres and Village Green Subdivisionsrespectively(Harmsen, 1989)
Water levels were then measuredin the wells using a fiberglassreinforced tape with
an attachedpopper. Local hydraulic gradient and principle groundwaterflow
direction were determinedfrom this information
Two transectsparallel to groundwaterflow were then establishedin each
subdivision. Along each transectfour multipart wells were installed to monitor
changesin groundwaterquality as water passedfrom one end of the subdivision to the
~r.
Multiport well constructionwas basedon a designby Bradbury and Bahr (1987).
The wells consistedof a 1.27 cm (0.50 in. PVC spine surroundedby up to eight,
0.635 cm inside diameterpolypropylenetubes. The tubeswere attachedto the PVC
30
center spine with nylon reinforced tape. An attempt was madeto screenthe spine
with a slotted PVC screenedinterval at the watertable. Each tube extendedto a
different depth in the aquifer and was perforatedwith 0.32 cm (l/g in) holes over its
last 15.25 cm (6 in.) and wrappedwith a nylon fabric. This fabric servedas a screen
to exclude the finer textured materialsfrom entering the well port. This well design
(seeFigure 2) allowed discrete samplesto be taken from various depthsin the
aquifer. When installed in transectsparallel to flow, thesesampleshelpedto
distinguish betweensubdivisionimpactedwater and upgradientwater as the water
moved from one end of the subdivisionto the other. Samplingports were placed at
approximately0.75, 1.5,3.0,4.5,6.0,
and 7.5 m below the watertable. The up and
downgradientwells of one transectat each subdivisionhad additional samplingports
at approximately9.0, 12.0, and 15 m below the watertable(Harmsen, 1989).
In the Jordan Acres subdivisionthe east transectcontainedfive wells, insteadof
the typical four. The furthest downgradientwell in this transect(E5) was locatedon
a small knoll. The well was not constructedto accountfor the changein topography,
causingthe upper two samplingports to be locatedabove the watertablethroughout
the duration of the project. As a result, no water sampleswere collected from those
ports. Another multiport well in the Jordan Acres Subdivision (JA-C) was locatedat
the downgradientend of the subdivisionbetweenthe two transects. Figures 3 and 4
show the basic subdivisionlayouts and well locationsfor the Jordan Acres and Village
Green Subdivisionsrespectively.
The multiport wells were then surveyedto the samearbitrary datum as the
surveywells, so all elevationswererelative. From this, a moredetailedflow map
31
]
=
=
~
=
-
"'
CJ
.Q.
OJ
~
"'
~
...
OJ
:=
~
S
r.,.
0
=
0
.=
CJ
0
-
~
0
~~
.r/]
A.
~
.A.
.-
,--
=c
.>~
.
-?
'"
I
U
~
.
=
i
...
-
08...
00 .-
-
S
,...
~=
=
=
d
., .,'..."
..
...'"
D&.~
\
~
.,
0:
,-? ~
..-;>
11\
=
r--
"'O~
~.
"'
~
.
~
'"
~
.-~
""
Q
~
"
~ 0
D
-
,?
"'-.:.."'!..
n
~
'"
~
,--
=
11\
~
~
-
'"
~
1ft
i
Q
a
E
~
-<
~
III
C
~~
~
=C)
~
<I'
-
...
~
~
&.u Q
~.., ;~ ~
I
.,
r-
..,
~
~
,..;;
""
Q
~
I-
~
~
.;~'"
n
.,.-
I-
.8 r
=
.-
C.)~
-< -c
1'1
n
'"
"
x
'"
.,.
!
III
,..
N
.,
.~
r--
~~
0...
~
i"'
.
~
=
'"
I
~ OJ
"
~./'
"
~
"
UJ.~
0
~
..
.,.
Q
.-
...c~
~~
cO-
~
!"
""O~
Q)
OJ
-=
-
II
.?
.
"O:!
"" C)
Q ~
~
~
r..) .s
""
~ Q
""i
.i Q
~ a
33
=
=
~
.!
.-
J
-
~
~
{Ij
:'
~
~
~
."3
e
~
=
=
=
~
-g
~
.c
~
.-=
~
=
.c
{Ij
.;;:
=
~
~
=
~
~
~
.5
=
.a
=
e
=
~
~
~
~
.
~~
= ~
.~
>~
. =
~ 'C
~ =
--a
~=
s
e
During the summerof 1988 severaladditional wells were installed in both
subdivisions. Thesewells were installed in an attempt to quantify the impact
individual septic systemsand lawns were having on groundwaterquality. This
information was determinedto be necessaryfor better estimationof the total nitrogen
input for a massbalancecomputer model, BURBS (Hughesand Pacenka,1985),
being used for the subdivisions.
Five septic systemsand one lawn from each subdivisionwere selectedfor
detailed monitoring, Each septic systemand lawn was instrumentedwith an
upgradientand at least one downgradientwell, with respectto groundwaterflow.
Thesewells were of similar constructionto the survey wells exceptthat the 3.18 cm
(11/4in) PVC pipe had threaded,rather than solvent weldedjoints. Threadedjoints
were determinednecessaryto avoid potential VOC contaminationassociatedwith the
solvent welding technique. The well screensusedin the constructionof thesewells
were also longer, 91.44 cm (36 in), and were positionedto intercept the water table
in most instances. Downgradientseptic and lawn wells were positionedas close to
the septic drainfield or lawn as the geographiclocation and the homeownerwould
allow, generally within 6 m (20 ft).
During the summerof 1989 severalmore monitoring wells were installed in both
subdivisions. The wells were positionedat key locations where additional water
quality information was determinedto be beneficial to the objectivesof the study.
In Village Green five more multiport wells were installed, four in a transect
perpendicularto groundwaterflow at the downgradientend of the subdivision (WA-I
through-4), and one upgradient(LC) to better define incoming and exiting water
35
quality. Figure 4 showsthe location of thesewells.
Two additional multiport wells were also installed on the downgradientend of
the Jordan Acres subdivision. Thesewells (GRE and LIP) were installed to better
quantify the impact the subdivisionwas having on groundwaterquality. Figure 3
showsthe location of thesewells. Thesemultiport wells were constructedin a similar
fashion to the original multiport wells except that the screenedintervals of the
polypropylene tubeswere wrappedwith TYPAR rather then nylon. The wells also
differ in that the center spine of 1.27 cm (0.5 in) was screenedoyer its last one foot
interval insteadof a five foot sectionnear the watertable. The wells were all
approximately21.3 m (70 ft) deepwith 8 or 9 poly tube ports and the one foot
screenedport at 21.3 ffi, as shownin Figure 5
The multiport wells were installed with the assistanceof the Wisconsin Geological
Figure 5. Designof 23 meter deepmultiport monitoring wells.
36
andNaturalHistory Surveycrewanddrill rig, a truck mountedrotary drill rig
utilizing a 10.16 cm (4 in) I.D. hollow core auger, The wells were constructedat the
site and were insertedinto the hollow stem auger once the proper depth was obtained.
The well was then usedto tap out a plastic plug at the tip of the lead auger. The plug
was necessaryto keep cuttings from entering the hollow portion of the auger during
the drilling process,and was left in the bore hole when the augerswere removed,
The annular spacebetweenthe inside of the auger and the well was kept full of water
during auger removal to prevent saturatedaquifer material from surging up into the
auger, Water was obtainedfrom nearbyprivate wells at the Jordan Acres well sites,
and at the upgradientsite in Village Green, A separate5.08 cm (2 in) well was
installed to supply water at the downgradientsites in Village Green. This well
(WLR) was screenedwith a 91.44 cm (36 in) slotted (0.0254 cm) screenwhich was
positioned approximately m below the watertable, A Stevensmodel water level
recorder was later installed at this location to continuouslymonitor watertable
fluctuations.As the augerwasremovedfrom the borehole, the aquifermaterial
collapsedinward around the well up to the watertable. The bore hole was back-filled
with sandremovedduring the drilling processfrom the watertableto within 1-2 m of
the surface. The last 1-2 m of the bore hole was sealedwith a powderedbentonite
clay.
Onceinstalled,the wells wereprotectedby driving a 1 m long, 15.25cm
diametergalvanizedsteel culvert down around them. Typically 0.3 meterswas left
protruding above ground level and the culvert was securedwith a locking cap,
In addition to the above mentionedmultiport wells, two nestedwells (REC and
37
REW) were installed at a septic study site (REE) in Jordan Acres during the summer
of 1989. The wells were installed downgradientof a septic systemwhich had been
instrumentedwith up and downgradientwells the previous summer. Water samples
from the initial wells had shown little difference betweenthe septic up and septic
downgradientwater chemistry. This was the casefor four of the five septic system
monitoring well sites at Jordan Acres. This site was selectedfor additional
monitoring becauseof its location on the upgradientend of the subdivision,
homeownercooperation,and ample spacefor the installation of more wells. These
two wells (REC & REW) were installed in an east-westtransectwith the existing
downgradientwell, 4.9 m (16 ft.) away from and parallel to the downgradientedgeof
the drainfield,as shownin Figure6. It wasbelievedthat thesewells would show
whether or not preferential percolationwas occurring out of this system,or if strong
vertical flow componentswere transportingcontaminationdeeperinto the aquifer and
below the existing monitoring well.
Thesewells were of a different designthen any of the wells installed in the
subdivisionsto this point. The wells consistedof three 1.91 cm (3/4in) PVC pipes
tapedtogether with nylon reinforced tape. The threadedjoint pipes were screened
with 30.48 cm (1 ft) slotted, 0.025 cm (0.10 in) slot size, PVC points. The screens
were positionedat 15.24 cm (6 in) intervals, with the lower portion of the uppermost
screenbeing placed at the watertable,as shown in Figure 7. This well designproved
very effective at accountingfor seasonalwatertablefluctuationsand changingplume
configurations.
During the summerof 1990, five more multilevel monitoring wells were installed
38
N
I
RSDS-A
RSDS-B
RSDS-C
.
_~CAL~
15
_tA,.g
I
t
.
.
RSDS-D.
RSDS-E
.
Figure 6. Location of wellsat Jordan Acressepticstudy site REE.
Figure 7. REC and REW well design,includesshallow,medium and deepports,
located4.6 m downgradientof the site REE drainfield.
39
at site REC. Thesewells were installed in a transectperpendicularto groundwater
flow, with well "B" being positioned33.5 meters(110 ft) downgradientof well REC,
with 3.05 m (10 ft) of separationbetweeneachof the five wells as shown in Figure
6. The wells were constructedsimilar to the multiport wells excepta 1.91 cm (3/4in)
spine was used to allow water-level measurements
to be madewith a tape and popper.
As with the multi-ports, the spine was screenedover its last 0.3 m (1 ft) interval with
a 30.48 cm (1 it) slotted point with 0.025 cm openings. The polypropylenetubes
were perforated and screenedwith TYPAR over a 25.4 cm (10 in) sectionat the
bottom of each tube. Four of the wells (A,C,D,E) have five samplingports,
including the spine, at 30.48 cm (1 ft) intervals. This equatesto 5.08 cm (2 in)
separationsbetweenthe screenedintervals. The upper most screenedinterval was
positionedat or just below the watertable,so the wells were capableof sampling the
upper 1.5 m (5 ft) of the aquifer at 30.48 cm (1 ft) intervals over a 12.2 meter wide
transectas shownin Figures6 and8. Well "B" had two additional samplingports as
shownin Figure 8.
During the summerof 1991 one additional well (KEP) was installed in the
Village Green subdivision. The purposeof this well was to determineif saturated
zone attenuationof phosphorusand fluorescencewas occurring and to evaluatethe
nitrate-N:chloride ratio in the plume at this location. The well was constructed
similar in style to the above mentionedRSDS wells excepta 3.17 cm (11/4in) spine
was used with a 91.44 cm (3 it) slotted screenhaving 0.025 cm (0.10 in) openings.
Three polypropylene tubeswere perforatedover 15.24 cm (6 in) intervals and
wrapped with TYPAR fabric. These screenswere positionedat intervals of 15.24
40
Elev.
98
(ft..)
80
79
78
77
76
75
74
73
72
Figure 8. Cross sectional view of RSDS wells, .view is from down to upgradient.
Wells are located 38 meters downgradient of the drainfield at site REE. Hash
marks representthe center of the 30.5 cm samplinginterval.
cm as shownin Figure9. The well was installed with a bucket auger 29 m (95 it)
downgradientof the septic drainfield vent as shown in Figure 6.
The multiport samplingwells describedaboverequired very little well
developmentbefore sedimentfree sampleswere produced. Due to the small well
volumes, thesewells also tendedto purge quite rapidly even at low pumping rates.
The PVC wells weretypicallydevelopedwith a largeperistalticpumpor with a
gasolinepowered impeller-type pump. A hoseattachedto the pump was then surged
up anddownin the well in an attemptto removeor displacethe finer textured
formation deposits. The well was assumedto be developedwhen this process
produced sediment-freewater.
41
Figure
9. Design of KEP well, downgradient of site BAR in Village Green.
Groundwater Sample Acquisition
The peristaltic pump usedto obtain groundwatersampleswas a Cole-Parmer,
dual-headed,l2-volt DC electric pump. The pumping lines (the only wetted part)
were silica tubing.
The multiport wells were sampledby attachingone of the pump's influent lines
directly to the individual tubes, then withdrawing the water by vacuum. Becausethe
pump had two separatepumping heads,two wells were frequently pumpedat the
sametime. To samplethe other types of wells, a length (or two) of O.64-cm(lA-in)
O.D. polypropylene tubing was lowered into the well, and the samplewas withdrawn
with the pump. The wells were purgedprior to samplingby removing at least three
times the volume of the well, or until constanttemperatureand conductivity readings
42
were obtained.
Field pH and conductivity measurements
were obtainedby directing the pump
effluent into the appropriatemeasurementcontainer. The water was allowed to flow
over the instrument's detectoruntil a constantreading was obtained, at which time the
value was recordedin a field notebook.
After the pH and conductivity measurements
were obtained, the sampleswere
filtered. Filtering was accomplishedby using a Gelmanin-line filtering cartridge and
0.45 micron filters. At least 200 ml of water was allowed to passthrough the filter
prior to obtainingthe sample.The filtered samplewasdischargeddirectly into a 250
ml Nalgene samplebottle or other suitablesamplecontainer.
Samplesfor trace organic analysiswere collected from monitoring wells by using
a Teflon bailer after the well was purged with a peristaltic pump. The bailers were
made of 1.5-m (5-foot) lengths of 2.54-cm (I-in) diameterTeflon or Schedule40
PVC with a ball check-valvein the bottom. The bailer was lowered into the well
usinga lengthof nylon rope. Three times the well volume was purged prior to
obtaining the sample. Samplesfrom multilevel wells were collected using a peristaltic
pump. All sampleswere kept on ice until delivery to the ETF lab.
Inorganic Chemical Analysis
Groundwatersampleanalyseswere performed by the ETF lab at the University
of Wisconsin-StevensPoint (Wisconsinlab certification #750040280).
Nitrate-N, chloride, and reactive phosphorouswere analyzedusing a Technicon
Autoanalyzer. Nitrate-N analysisuseda sulfanilamidecomplex read at 520 nm
(MethodNo. 158-71W/A). Chlorideanalysisuseda ferricyanideion readat 480 nm
43
(Section407D, APHA, 1985). Reactivephosphorousanalysisuseda
phosphomolybdenum complex read at 880 nm (Industrial Method No. 329-74 W/B)
Sodium analyses were performed using a Varian AA475 Atomic Absorption
spectrophotometerread at 589.0 nm.
Analyses for alkalinity and total hardness were performed using techniques
described in Standard Methods for the Examination of Water and Wastewater (APHA
et aI., 1985).
Relative fluorescencewas measuredusing a Baird-Atomic Fluoripoint. The
excitation scanwas set at 355 nm and the emissionwas set at 425 nm.
The pH and specific conductancewere measuredin the field using a Coming
electrodemeter (PH) and a YSI conductivity cell.
Organic Chemical Analysis
The groundwater samples collected from the potable, irrigation, and monitoring
wells were analyzedin the University of Wisconsin-StevensPoint, ETF laboratory
The groundwater samples were analyzed for some or all of the analyte groups listed
below.
Volatile organic compound (VOC) analysis was performed using EPA Methods
5030/601-602. This is a purge and trap extraction method, utilizing a photoionization
detector(Pill) with a 10.6 eV lamp and an Hall electrolytic conductivity detector
(HECD)
,
.
set ill halogen mode.
The detectorswere set up to run in-series. with the
HECD following the PID.
Polynuclear aromatic hydrocarbon (PAH) analysis was performed using the high
pressureliquid chromatographic(HPLC) methodin EPA Method 610. The HPLC
44
systemconsistedof an automatedsampleinjection system,a temperaturecontrolled
reversephasecolumn, and an ultraviolet (UV) detectorand florescencedetectorin
senes.
Semi-volatile organic analyseswere performed on severalof the groundwater
samples. An electron capturedetector(ECD) was usedto screengroundwater
samplesfor semi-volatileorganic compounds. A thermoionic specific detector (TSD)
was used to screengroundwatersamplesfor semi-volatileorganic compoundsthat
contain nitrogen and phosphorous. The samplesfor both analyseswere extracted
following EPA Method 608, and analyzedby gas chromatography. The samplewas
injected into the gas chromatographand split betweentwo columns, each going to a
separatedetector. A temperatureprogram was usedto aid in compoundresolution
45
D. Surveyof HomeownersChemicalUseand Attitudes
(Condensedfrom Mechenichet. al., 1991)
Introduction
Questionsabout the effects of unseweredresidentialareason groundwater
quality are being raised by groundwaterplannersand regulatorsin Wisconsin and
many other states. To make good decisionsabout potential impacts, more information
is neededabout the activities of thoseliving in theseareas, such as lawn fertilization
and householdchemical use and disposalpractices.
A number of studiesdocumentinggroundwaterpollution problems from
unseweredsubdivisionswere reviewed by Bicki and Brown (1991). Most studiesthey
reviewed reported that a minimum lot size of 0.2 to 0.4 Ha (0.5 to 1 acre) was
neededto prevent nitrate-N contaminationof groundwater. However, they also noted
that in someareaseven larger lots were inadequateto prevent contamination, These
lot sizeswere basedon neededseparationof onsite waste disposalsystems.
Nitrate-N contaminationof groundwaterfrom fertilizer was not specifically
addressed. However, severalauthorshave reported significant leaching of nitrate-N
from fertilized turf grass (Morton et aI., 1988; Owen and Barraclough, 1983; Rieke
andEllis, 1974). The recommendedminimum lot sizesalso did not accountfor
potential effects of pesticidesusedon lawns and gardens,or volatile organic or other
toxic compoundsfound in householdcleaning and maintenanceproducts. Cleaning
products usedin homesoften contain solvents,disinfectants,and other potentially
hazardouscompounds. Commonly usedproducts such as laundry detergent,toilet
bowl cleaner, and tub and tile cleanersmay contain a variety of chemical compounds
46
classified by the U. S. EnvironmentalProtection Agency as priority pollutants
(Hathaway, 1980).
Many factors influence the extent to which use of theseproductsby residentsof
unseweredsubdivisionsrepresenta hazardto groundwaterquality. Theseinclude the
chemical compositionof the product, the volume used, and the methodof disposalin
addition to soil and aquifer attenuationpotential. Volatile organic compounds
disposedof in onsite sewagedisposalsystemshave been reported to have reached
groundwaterby severalresearchers(Tomsonet aI., 1984; Kolega et aI., 1986).
This report, part of a larger researchproject on the effects of unsewered
subdivisionson groundwaterquality, details chemicaluse practicesand attitudesabout
groundwatercontaminationand managementin two subdivisionsin Central
Wisconsin; Jordan Acres and Village Green Estates,
The two subdivisionsare locatedin PortageCounty, in the northern portion of
the Central Wisconsin sandplain (Figure 1). JordanAcres is located about 5.2 kin
northeastof the city of StevensPoint, and Village Green is about 2.6 km southeast.
The averageageof the homesin the two subdivisions
is 15 to 16 years,with the first
homesbeing built in the 1960s. JordanAcres had 64 developedlots, with an average
lot size of 0.2 Ha (0.6 acres). The averagevalue of homesin Jordan Acres in 1990
was $58,000, with a range of $38,000 to $86,000. Village Green had 136 developed
lots with an averagesizeof 0.16 Ha (0.4 acres).The averagevalueof homeswas
$62,000, with a range of $47,000 to $123,000.
The geologic setting and groundwater pollution potential for both subdivisions is
similar. A sandand gravel aquifer underliesboth subdivisionsto a depth of
47
approximately26.2 m (80 ft), with a water table depth of 6.6 to 8.2 m (20 to 25 ft).
However, contaminant sources upgradient of the two subdivisions are somewhat
different. A small amount of agricultural activity occurs upgradientof Jordan Acres,
whereasmuch of the land upgradientof Village Greenis intensively irrigated
agricultura1land, used primarily for potato production.
Within the two subdivisions, groundwater contamination problems have already
occurred. The averagenitrate-N concentrationin private wells testedin Jordan Acres
from 1976 to 1988 was 6.8 mg/l; in Village Green,
.3 fig/I.
Village Green had 16
samplesexceeding20 mg/! during that time period (EnvironmentalTask Force,
1989).
Objectives
The objectivesof the homeownersurvey were to:
1)
characterizethe amountsand variety of productsusedfor household
cleaning and maintenance,and lawn and gardencare, in two unsewered
subdivisions;
2)
evaluatethe hazardto groundwaterfrom use of theseproducts, including their intrinsic hazardsand the hazardscausedby use or disposal
practices, and to provide data to researcherssiting monitoring wells;
3)
collect nitrogen loading data for use by other researchersin a mass
balancemodel;
4)
understandhow residentsview the causesand severity of groundwater
contaminationin their county and neighborhood,and how they might
respondto various solutions;
5)
examinethe relationshipsbetweenresidents'beliefs about groundwater
contaminationand chemical use practices;and
6)
evaluateareasof greatestneed for educationalefforts.
48
Survey Results and Discussion
Chemical use data obtainedfrom the surveysare groupedby uses; household
cleaning products, maintenanceproducts, and lawn and gardenchemical use.
Following discussionof eachgroup, relationshipsbetweenthe groups are examined.
Attitudes and opinions about groundwaterprotection are then discussed.
Household Cleaning Products Use
Commonly usedproducts such as laundry detergent,toilet bowl cleaner, and tub
and tile cleanersmay contain a variety of chemicalcompoundsclassified by the U.S,
Environmental Protection Agency as priority pollutants. One objective of this survey
was to characterizethe types, amounts,and variety of productsused for household
cleaning and maintenancein the subdivisions Participantswere askedto specify, by
brand name, the productsusedin their householdfor bathroom and kitchen cleaning,
laundry care, and septic systemmaintenance. They were also askedto specify the
frequencyof use, Theseproductshave a high probability of ending up in the septic
tank through normal use.
Only one statistically significant difference (p
< 0.05) wasfoundin userates
betweenthe two subdivisions. Bathroomrust and lime remover was used
significantly more often in the Village Green subdivisionthan in Jordan Acres. This
may be related to the differencesin total hardnessof water betweenthe two
subdivisions. Samplesfrom Village Green averaged165 mg/l total hardness,reported
as CaCO3,with somevaluesas high as 250 mg/I, In Jordan Acres, total hardness
averaged108 mg/1as CaCO3,with a maximum of 140 mg/l. Iron concentrationsare
49
Product
Drainfield
root killer
Laundry rust remover
Drain cleaner
Carpet cleaner
Septic system additives
Bathroom rust/lime
remover
Bathroom floor cleaner
Chlorine bleach
Kitchen floor cleaner
Garbage disposal cleaner
Grease cutting spray
Toilet bowl cleaner
Bathroom spray cleaner
Powdered laundry sanitizer
Kitchen cleanser
Bathroom cleanser
Powdered bleach
Spot remover
Laundry detergent
Avg number of
uses/month in
one home
0.08
0.21
0.54
0.68
0.98
1.35
2.50
3.28
3.51
3.57
3.60
4.19
4.20
4.61
4.65
4.99
6.83
7.13
15.66
Number
Number
~
0.08
0.08-0.33
0.03-4.0
0.08-4.0
0.08-4.0
0.08-4.0
0.08-8.0
0.17-30
0.25-60
1.0-10.0
0.17-15
0.25-30
0.17-15
0.17-12
0.37-30
0.5-30
0.33-40
0.5-20
2-60
of
Percent
of
uses/month
~
~
1
2
45
18
18
19
97
72
92
7
53
110
101
6
92
96
35
41
114
<1
1
34
13
13
14
72
54
69
5
40
82
75
4
69
72
26
30
85
0
24
12
17
24
237
265
316
25
184
453
417
28
419
469
232
277
1751.
Table 3. Number of usersand averageuserates for householdcleaningproducts
in two PortageCounty subdivisions.
not a significant problem in either subdivision. Despitethe difference in water
hardness,use of other cleaningproductswas not significantly different, so cleaning
product use data for the two subdivisionswas reported together.
Someproductswereusedfrequentlyby thosewho reportedusingthem. Laundry
detergentwas usedan averageof 15.7 times per month, followed by bathroom
cleanser,used an averageof 5.0 times per month (Table 3), Other products, although
usedslightlylessfrequently,werealsousedby a largenumberof participants.For
example, toilet bowl cleanerwas usedby 110 participants(82%), and bathroom
cleanserwas usedby 96 participants(72%). Laundry detergents,toilet bowl cleaners,
and bathroom cleansersare the top three productsusedby homeowners.
50
Large use rangeswere observedfor many products. For example, people
reported using chlorine bleach anywherefrom twice a year to every day. Such wide
variations make generalizationsabout use rates difficult.
Another way of evaluatinghouseholdproduct use is to categorizeusersby
quartiles as high, medium-high, medium-low, or low users. High userswere those
using householdcleaningproducts54 times per month or more; medium-high, 35-54;
medium-low, 26-35; and low, less than 26 usesper month. Subtractinguse of
laundry detergentfrom the totals, high userswere thoseusing householdcleaning
products 34 times per month or more; medium-high,22-34; medium-low, 14-22; and
low, less than 14 usesper month.
To provide a clearer picture of householdchemical use, the total number of uses
per month was calculatedfor eachproduct. This illustrates that someproducts (root
killers, rust removers)are usedinfrequentlyby only a few people. Others,suchas
laundry detergentand bathroomcleanser,are usedoften by the majority of
participants. However, someof the productsusedinfrequently, such as septic system
additives and wood cleaners,may be intrinsically the most hazardous.
The numbersof bathroom and kitcben cleaningproductsusedranged from two to
nine, with most userslisting four to six productsas the typical number used.
Cleaning frequenciesfor theserooms averageonce per week, but somereported
cleaning daily
Thesedata were usedto help designa monitoring strategyfor priority
pollutants in groundwaterunder the subdivision,both for individual homesand in the
aggregate In addition, an educationalstrategypresentingsubdivisionresidentswith
51
information about the most hazardousproductsand safe, effective alternatives,with
emphasisgiven to those most frequently usedby large numbersof people, may reduce
the risk of groundwatercontamination.
Household Maintenance Products
Information on use of wood oils and cleaningproducts, paint thinner and
strippers, car maintenanceproducts, and "others" were also gathered. Theseproducts
do not commonly enter septic systemsthrough use, but may be improperly disposed
of there. They may alsobe disposedof on the ground,andcouldcontributeto
groundwatercontaminationin that way.
Both frequencyof use and number of usersare lower for this category of
products (Table 4) However, the methodof wastedisposalmay be a significant
concern. Paint thinner, paint stripper, and oil were all reported to have been disposed
Product
Average
number of
uses/month
Max
Number
of users
Percent
Using
4
25
18
7
5
Paint thinner
.87
Paint or varnish
.66
Paint
56
2
43
31
Motor oil
,66
2
49
35
Antifreeze
.32
1
15
11
Metal cleaners
77
1
4
3
2.10
4
13
9
78
4
12
9
Wood oils
Wood cleaners
Table 4. Use of selectedmaintenanceproductsin two PortageCounty
subdivisions.
~?:
of in the septic systemor the yard (Figure 10). However, it appearsthat most oil
waste and at least half of paint thinner and stripper is disposedof through meansnot
directly linked to the subdivisiongroundwatersystem
Educationalefforts in this category should focus on proper disposalpracticesfor
hazardousproducts
-60
so
U)
L
Q)
U) 40
0
0U)
°30
\tO
L
Q) 20
~
:)
Z
10
0
Septic
System
Yard
Other
011
Figure 10. Number of participants reporting various disposal practices for paint
thinner, paint stripper and motor oil in two Portage County subdivisions.
Lawn and Garden Chemical Use
Lawn fertilization and pesticideuse on lawns and gardensare also potential
threats to groundwaterquality in subdivisions. Another objective of this survey was
to characterizethe frequencyand volume of lawn and gardenchemical use in these
subdivisions. Questionswere askedabout homeownerapplied and commercial
applicator applied fertilizer and pesticides. In this section, comparisonsare often
5~
made betweenoverall use rates, which include all survey participants, and the use
rates of "users", or those who actually reported using the product being discussed.
Nine participants (6 %) reported never fertilizing their lawns and never having
them fertilized by a lawn service. Most people reported fertilizing their own lawns
once or twice a year. The meanfertilization rate for the subdivisionsoverall was 1.6
times per year, (1.8 times for users)with a range of once every five years to four
times per year (Figure 11). Seventy-fourpercent statedthat they use the amount
specifiedon the bag when fertilizing; 18 percentreported using more. Only two
participantsreported not reading the bag at all when applying fertilizer. This data is
usedlater in the report for input to the massbalancemodel. Seventy-twopercent of
usersreported using a fertilizer with a nitrogen contentof 26 percent or greater.
Thirty-five percent reported using a slow-releasenitrogen fertilizer, but 50 percent did
not know if their fertilizer was of this type. Forty-nine percent reported using a
mixture of broad leaf weed killer and fertilizer (weed and feed) on their lawns. The
averageuserate was0.8 timesper yearoverall,with an averageuserate of 1.2 times
per year reported by users. Thirty-one participants(22%) reported never using this
product, while the 68 usersreported frequenciesof use from once every five years to
three times a vear. Crabgrasskiller was applied an averageof once per year by 31
users (22%), with a range of once every five years to twice annually. The overall
averageuse rate (including nonusers)was 0.3 times per year.
Application frequenciesfor fertilizer reportedby fertilizer userswere not
significantly different (p < 0.05) betweenthe two subdivisions(1.6 per year for
JordanAcresand 1.8 per yearfor Village Green). However,the overalluserate
~i1
(including nonusers)for the two subdivisionswas significantly different (1.3 per year
for JordanAcres, 1.7 per yearfor Village Green)(p < 0.05). This differenceoccurs
becauseof the nine non-usersof fertilizer, six live in Jordan Acres, accountingfor
twelve percent of Jordan Acres participants. In Village Green, only three percentof
participantsdo not fertilize. The samerelationship (non-significantdifferencesfor
usersbut a significant dif.
overall) was observedfor broad leaf weed killer
(weed and feed). . No significant difference was found for crabarass
control products.
b
-en
(/)
I.. 40
Q)
~
"0
30
I..
Q)
~
:J
?
20
--
--~~-
Never
n."-1
1.1-2
I J~p~/ Yp~r
Fi
11. Frequency of lawn fertilizer use in two f
County subdivisions.
Other common lawn care practicesincluded mowing the lawn once per week
(69%), with 14 I
t mowing more frequently. Sixty-six percent removedlawn
clippings after mowing Forty percentwateredtheir lawnsan averageof oncea week
during the growing
I, while 13 percentreported never
.ng (Table 5)
55
Waters once per
week or more
Mows once per
week or more
(%)
Removes lawn
Jordan Acres
59
68
48
Village Green
79
91
76
Combined
71
83
66
Fertilizer
applications/yr
(%)
Uses Weed and
Feed
(%)
clippings
(%)
Uses
Insecticides
(%)
Jordan Acres
1.6
44
54
Village Green
1.8
52
47
Combined
1.8
49
50
Table 5. Lawn care practicesreported in two PortageCounty subdivisions.
Relationshipswere apparentbetweenvarious lawn care practices. For
example, 24 percent of thosewho fertilize more than twice a year mowed their lawns
more than once a week, while none of thosewho never fertilized mowed their lawns
that frequently. Over 80 percentof thosewho fertilized more than twice a year
removedtheir lawn clippings, comparedto 44 percent of thosewho never fertilize.
All three participantswho water their lawns daily fertilize more than twice a year,
while the majority of thosewho never fertilize,' never water either. Statistically
significant relationships(p < 0.05) were found betweenlawn fertilization frequency
and mowing frequency, removing clippings, and watering frequency,
Cluster analysisindicatesthat lawn care practicescan be divided into two
groups. The first group, which usedless fertilizer, was also likely to mow less
frequently, was less likely to remove clippings, and wateredtheir lawns less often
than thosein the secondgroup.
56
Only ten participantsreported using a commerciallawn care service. Of those,
three reported that the service never applied any lawn chemicals,including fertilizer.
These may have been strictly lawn mowing services. Of the remaining seven,two
reported monthly fertilizer application, and two reported semi-annualapplication, with
the other four giving no response. A total of sevenreported use of herbicides, with
applicationsof three twice a year and four once a year. Three reported application of
insecticides;two twice a year and one once a year. Only one participant reported the
use of fungicides.
Study participantsreported to use insecticidesless frequently than other lawn
and garden chemicals. The most commonly usedinsecticideswere diazinon (usedby
51 participants), malathion (usedby 16), and carbaryl (Sevin) (usedby 17). Most
reported using small amounts(less than one cup of undiluted product per year) but
someused more than 10 cups per year (Figure 12)
Of the insecticideschosenby subdivisionresidents,diazinon is reported to
have a medium potential for leaching to groundwater,and carbaryl and malathion
have
a low
potential
(Becker
et ai,
1990).
,
From
1983
to
1987,
the Wisconsin
Depart-
ment of Natural Resourcespesticidemonitoring report showsthat five of 230 sampled
wells containeddetectablelevels of carbaryl; none of four sampledwells contained
malathion; and none of 27 wells containeddiazinon (WDNR, 1987). Pesticidemixing
and disposalpracticesin the subdivisionswere not specifically surveyed,but there
may be somepotential for groundwatercontaminationfrom thesepracticesas well as
from routine use.
57
-:1n
':IS
U}
~ 20
~
\I0 15
~
L
Q)
..0
E 10
::}
~
~
"
nil'l~in()n
0-1 cups
11-2
cups
001!
2-5 cups
5-10
cups
> 10 CUPS
Figure 12. Type and amounts of insecticidesused in two Portage County
subdivisions.
To minimize fertilizer loss, educationalefforts on lawn and g.
practices
could be focusedon the benefits of modifying lawn care practices, such as leaving
grassclippings on lawns and limiting irrigation. Participantsmight also benefit from
comparisonof their fertilizer applicationrates with the rates usedby farmers to grow
crops. Many people 1
insignificant co.
ve their fertilizer application on lawns to be
to agricultural applications,but this is not always the case.
More information on the relative im]..
.ce of fertilization practicescomparedto
other sourcesof groundwatercontaminationin the subdivisionscan be found in
SectionI. Participantsmay also needinstruction on proper pesticidemixing, storing
and disposalpractices.
58
Knowledge about Water Supplies and Septic Systems
Participantswere askedfor somebasic information about their well and
sewagedisposal system. Wells in the two subdivisionsare generally similar in
construction: shallow driven-point wells with an averagedepth of 8.7 meters
Minimum well depthsreported were 4 metersin JordanAcres and 4.3 metersin
Village Green. The deepestwells in the subdivisionswere in the 13 meter range,
although one person reported an estimateddepth of 25 meters. The averagedepth to
water is 5.3 meters. Only 25 participants(18%) were certain of the well depth
information they reported. This probably reflects the fact that in Wisconsin, no
record-keepingon driven-point wells was required at the time of the survey.
Seventeenparticipants(12%) reported that their wells had been replacedor upgraded
since original construction, 6 in Jordan Acres and 11 in Village Green.
Twenty-sevenparticipants(19%) reported that their sewagedisposalsystem
had been replacedsince original construction, 14 in Jordan Acres (28%) and 13 in
Village Green(15%). Participantsreportedpumpingtheir septictanksan averageof
every 1.9 years. Somereportedpumpingas frequentlyas onceevery six months,
,
while one participant reported an interval of 9 years. Overall, sewagedisposal
systemsare reportedly well maintained; 119 (86%) were pumpedat least once every
two years, and only five (4 %) were pumpedat an interval exceedingonce every three
years.
Educationalefforts about wells and septic systemsshould be focusedon the
importanceof gatheringand maintaininginformation about well depth, since depth
and constructionof wells is often related to the quality of the water they produce.
59
Well owners should also be remindedabout the importanceof regular water testing
although this practice was not specifically surveyed. It appears,however, that survey
participantshave a good knowledgeof proper septic systemmaintenance. In addjtion,
householdchemical use data and participant commentsshow that most have some
concernsabout the types of materialsthey disposeof as well
Attitudes and Opinions about Groundwater Issues
Participantswere askedto respondverbally to questionsmeasuringtheir
attitudesabout the severity and causesof groundwatercontaminationin their
subdivisionsand in PortageCounty. Overall, 63 percentof participantsstatedthat
groundwatercontaminationwas "a seriousproblem" in PortageCounty, while 13
percent ranked it as "a very seriousproblem." Only I percent felt that groundwater
contamination
was "no problemat all".
When respondingto an open-endedquestionabout the causesof this problem,
the words most frequently usedby participantswere pesticides(17%), ag fertilizer
(16%), farmers (14%), potato farmers (14%), and septic systems(6%). The greatest
concernsabout groundwaterquality were related,to nitrate-N and pesticide
contamination. At the time the survey was conducted,groundwatercontamination
with the potato insecticidealdicarb was a major issuein the county. Participants
apparentlyfollowed and understoodthe issuesin this contaminationincident, and believed the information being presented Overall, 67 percentof thosewho felt
groundwatercontaminationwas "serious" or "very serious" attributed the problem to
agriculture. Five percent attributed it to homeowners;24 percent said both were
equally responsible(Figure 13)
hO
Participants' assessment
of the severity of water quality problems in their own
subdivisionsvaried. In the Village Green subdivision, discussionof contamination
problems had occurred in the local media, and annexationof the subdivision to the
city had been discussed. In JordanAcres, water quality problems were fewer, and
there had been little public discussionabout them. Accordingly, 54 percent of Village
Green participantsranked groundwatercontaminationas a "serious" or "very serious"
problem in their subdivision. On the other hand, 77 percentof Jordan Acres
participantsrated it a "minor problem" or "no problem at all". In comparison,our
water quality survey showedthat 14 percentof wells in Jordan Acres and 43 percent
in Village Green exceededthe U.S. EPA maximum contaminantlevel for nitrate-N in
that sametime period, but participantsdid not have that information when completing
Figure 13. Participant responsesabout the major source of groundwater
contamination problems in Portage County.
61
the questionnaire.
In Jordan Acres, 73 percent of thoseranking it a "serious" or "very serious"
problem statedthat residentialland use was the primary cause,using words such as
homeowners(21%), lawn fertilizer (21%), septic systems(14%) and density (14%).
Twenty-sevenpercent attributed the problem to agriculture (Figure 14). On the other
hand, in Village Green subdivision, residentsperceivedthat agricultural as well as
residentialactivities were contributing to the problem. Thirty-nine percent of
participantsin Village Green attributed the problem mainly to agriculture, using
words such as Blue Top (a local feedlot) (11%), potato farmers (7%), and ag
fertilizer (7 %). Forty-three percent namedresidentialactivities, using words such as
septic systems(14%), lawn fertilizer (13%), and homeowners(10%) (Figure 14).
.Jordan
v
Acres
lage
Green
27%
996
73%
.
~
Agriculture
Homeowners
~
Both
n
Unknown
Figure 14. Reasonsgiven by participants that groundwater contamination is a
"serious" or "very serious" problem in two Portage County subdivisions.
62
Participantswere askedto choosefrom a list of problems they believed had
been experiencedas a result of groundwatercontaminationi&Portage County (Table
6). All the problems on the list were believed by the researchersto have ~ctually
occurred in the county. Problemsranked as the top three overall included loss of
clean drinking water (102 responses),loss of property values (99 responses),and
conflict betweenagricultural and residentialland uses(97 responses). Fewer people
believed the quality of life had beenlowered (33), that farm animals had been affected
(22), or that the area was less attractive to businesses(20).
Problems
All
Jordan
Acres
Loss of clean drinking water
102
44
Loss of property values
99
36
2
63
Conflict betweenag/residential
97
36
2
61
2
Buying/hauling water
74
26
3
48
4
Human stressor illness
52
26
3
26
6
Decreasedfish in streams
51
24
4
27
Lower quality of life
33
15
5
18
7
Farm animal illness/lower productivity
22
12
6
10
8
Area less attractive to businesses
20
10
7
10
8
Rank
Village
Green
Rank
58
Table 6. Problemsresulting from groundwatercontaminationin Portage
County.
The order of responsesvaried betweenthe two subdivisions,again perhaps
reflecting their differing experienceswith water quality problems, In Jordan Acres,
where few problems had beenexperiencedto date, "loss of clean drinking water" was
identified by the greatestnumber of participants On the other hand, in Village
Green, "loss of property values" was chosenby the greatestnumber of participants.
At least one participant directly statedto researchersthat reports of poor water quality
h~
had preventedthe sale of his home. The secondhighest selectionwas" conflict
betweenagricultural and residentialland uses", again perhapsreflecting participants'
perceivedproblems with a nearby feedlot
A set of twelve statementswas then presentedto participantswith a range of
answersfrom "strongly agree" to "strongly disagree"(Table 7). Responsesto several
of the statementswere similar in both subdivisions. About three-quartersof
participants(79 percentJordan Acres, 71 percentVillage Green) disagreedthat too
much emphasisis being placed on the problem of chemicalsin drinking water in
Wisconsin. Most participantsagreed(88 percentJordanAcres, 87 percent Village
Green) that educatingpeople on how their actionscausegroundwaterpollution is the
most effective solution to groundwaterproblems The majority of participants{85
percent Jordan Acres, 75 percent Village Green) also agreedthat individual actions
taken by a homeownercan make a significant difference in water quality in a
subdivision, and that homeownerscan pollute their own water supplies(94 percent
Jordan Acres, 88 percent Village Green).
Despite the fact that 23 percentof participantsin Jordan Acres felt that
groundwatercontaminationwas "a seriousproblem" in their subdivision, only 6
percent did not feel confident that their water was safe to drink, and 13 percent were
uncertain In Village Green, 76 percent felt confident that their water was safe to
drink, although 54 percent ranked groundwatercontaminationas a "serious" or "very
serious" problem in their subdivision.
Participantswere more neutral to the idea that laws are the only way to control
groundwatercontamination.In JordanAcres,52 percentagreedwith that statement,
64
Question
Too much emphasis is being placed on the problem of
chemicals in drinking water in Wisconsin.
I feel confident that my well water is safe to drink.
Educating people on how their actions cause
groundwater pollution is the most effective solution to
Strongly
Agree
(%)
Agree
(%)
2
18
(2)
(14)
Uncertain
(%)
14
(II)
Disagree
(%)
Strongly
Disagree
(%)
74
24
(56)
(18)
25
78
16
(19)
(60)
(12)
11
(8)
2
(2)
35
80
(27)
(61)
8
(6)
9
(7)
0
(0)
1
(1)
groundwater problems.
Laws regulating people and businesses are the only way
to control groundwater contamination.
17
47
23
44
(13)
(36)
(18)
(33)
Individual actions taken by a homeowner can make a
significant difference in groundwater in a subdivision.
28
76
17
11
(21)
(58)
(13)
(8)
Individual homeowners can cause the pollution of their
own water supplies.
31
88
12
1
(24)
(67)
(9)
(1)
Property values are being affected by water quality
problems in this subdivision.
22
41
24
41
(17)
(31)
(18)
(31)
One way to protect the groundwater in this subdivision
is if all the residents work together in controlling
contaminants.
0
(0)
0
(0)
4
(3)
0
(0)
22
94
10
7
(17)
(71)
(8)
(5)
3
(2)
22
6
69
31
groundwater quality.
(17)
(5)
(52)
(23)
Subdivisions with water quality problems should have
municipal sewer and water service provided by local
16
(12)
55
32
24
4
(42)
(24)
(18)
(3)
What we do in this household has no impact on our
government.
Annexation to the city of Stevens Point is an acceptable
option for obtaining municipal sewer and water service.
9
48
24
29
21
(7)
(36)
(18)
(22)
(16)
Having municipal sewer and water would increase the
value of my home.
20
67
17
21
7
(15)
(51)
(13)
(16)
(5)
Table 7. Responseto surveyopinion statements.
while 31 percent disagreed In Village Green, 47 percent agreed;36 percent
disagreed
A number of statementsdealing with the acceptabilityof receiving municipal
sewerandwaterserviceandaffectson propertyvalueswerealsopresented.Reaction
to thesein somecasesvaried significantly by subdivision. For example, in Village
Green, 64 percent agreedwith the statementthat "property values are being affected
by water quality problemsin this subdivision." In Jordan Acres, only 19 percent
65
agreed(a statistically significant difference, p < .05) In Jordan Acres, only 10
percent disagreedthat" subdivisionswith water quality problems should have
municipal sewer and water serviceprovided by local government", while in Village
Green, 23 percent disagreedand 5 percent strongly disagreed( also a statistically
significant difference). On the other hand, there was substantialagreementin both
subdivisions(69 percent in Jordan Acres, 64 percentin Village Green) that "having
municipal sewer and water would increasethe value of my home." On the
acceptabilityof annexationto the nearby city of StevensPoint, 27 percent of Jordan
Acres residentswere undecided,and a total of 25 percent were opposed, 13 percent
stronglyso. In Village Green,whereannexationhadbeendiscussed
asa real
possibility, a total of 46 percent were opposed,18 percent strongly so.
It is also informative to examinewhich opinion statementselicited the
strongestagreementor disagreementfrom participants. In Jordan Acres, the
statementmost often strongly agreedwith was "individual homeownerscan causethe
pollution of their own water supplies" (33%), foijowed by "one way to protect the
groundwaterin this subdivisionis if all the residentswork togetherin controlling
contaminants"(31%). Jordan Acres participantsmost often strongly disagreedwith
"What we do in this householdhas no impact on our groundwaterquality" (28%):
followed by "Too much emphasisis being placed on the problem of chemicalsin
drinking water in Wisconsin" (25%)
In Village Green, participantsmost often strongly agreedwith "Educating
people on how their actions causegroundwaterpollution is the most effective solution
to groundwaterproblems" and "Property valuesare being affectedby water quality
hh
problems in this subdivision" (each25%). As in Jordan Acres, Village Green
participantsmost often strongly disagreedwith "What we do in this householdhas no
impact on our groundwaterquality" (21%), followed by "Annexation to the city of
StevensPoint is an acceptableoption for obtaining municipal sewer and water service" (18%). It appearsthat fewer Village Green residentswere likely to feel
strongly about the above issues,but that they did react strongly to somewhich
personally affected them.
Educationalefforts to increaseawarenessof groundwaterproblems in Portage
County does not appearnecessaryat this point However, some subdivisionresidents
need to increasetheir awarenessof their own potential affects on their water supply
and need to assumesomepersonalresponsibility for it. There appearsto be a strong
feeling that working togethercan prevent groundwatercontamination Ways of
encouragingthat cooperationneedto be explored.
Relationships of Attitudes to Age, Gender and Educational Level
Severalattitude questionswere sigqificantly related to personalfactors such as
age, genderand educationlevel (p < .05). The question "Laws regulating people
and businessesare the only way to control groundwatercontamination", which previously was shown to have a significant relationshipto householdcleaning product use,
was also related to both genderand educationlevel, Fifty-eight percent of males
agreedwith this statement,while only 35 percentof femalesagreed. Among participants with a high school educationor less, 69 percentagreed,while of college
educatedparticipants, only 34 percentagreedwith the statement.
1;7
In responseto the statement"What we do in this householdhas no effect upon
our groundwaterquality", 31 percentof participantswith a high school educationor
less agreed. Only 1 percent of thosewith somecollege educationagreed.
Lastly, in responseto the statement"Annexation to the city of StevensPoint is
an acceptableoption for obtaining municipal sewerand water service", a significant
relationship to participants' age was found. Peopleage 45 and over were more likely
to agreewith the statement(59%) than thoseyounger than 45 (35%). Twenty-nine
percent of participantsyounger than 45 were uncertain, as opposedto only one person
in the 45 and older category.
Survey Conclusions
1.
Householdcleaning product use was similar betweenthe two subdivisions. Someproducts, such as laundry detergentand bathroom
cleanser,were usedat least weekly by most participants. Some
products which may be particularly hazardousto septic systemsand
groundwater, such as chlorine bleach, were also frequently usedby
participants.
")
Householdmaintenanceproducts suchas p,aintthinner and motor oil
were used less frequently and by fewer participants. However, there is
evidencethat thesematerialsare being improperly disposedof by some
participantsin ways that may adverselyaffect groundwater.
3
Lawn care practiceswere similar betweenthe two subdivisions,with a
meanfertilization rate of 1.6 times per year. Lawn fertilization
frequencywas related to mowing frequency, watering frequency, and
tendencyto remove lawn clippings.
4.
Insecticidesmost commonly usedincluded diazinon, malathionand
carbaryl, with nearly 40 percentof participantsreporting using
diazinon.
5.
Wells in the two subdivisionsare generally shallow driven points with
an averagedepth of 9 meters. Only 18 percent of participantswere
certain of the depth of their wells.
6R
6.
Participantsin the two subdivisionsgenerally reported following proper
sewagedisposalsystemmaintenance,with an averagepumping interval of 1.9
years.
7
A significant relationshipwas not found betweenlawn care and household
cleaning product use practices.
8.
Seventy-sixpercent of participantsbelieved groundwatercontaminationwas a
seriousor very seriousproblem in their county. Opinions about severity of
groundwatercontaminationin the individual subdivisionsvaried by
subdivision.
9.
Participantswere knowledgeableabout groundwatercontam~nationissues.
However, someneeda better understandingof how their own actions may
affect groundwaterquality.
10.
Although somerelationshipswere noted, in generalthere is not a good
relationshipbetweenhouseholdchemical use practicesand attitudes
about groundwatercontamination. A few relationshipswere found
betweenattitudesand age, genderor educationlevel.
69
E. Nitrogen MassBalancePredictionusing BURBSModel
One of the major objectivesof the project was to determinethe validity of using
massbalancenitrogen modelsto predict subdivisionimpactson groundwaterquality.
The BURBS model, developedat Cornell University by Hugheset. at. (1985) was
selectedfor use in this phaseof the project as it includesall the variables the authors
felt were significant to predicting nitrogen impacts to groundwater. The variables
usedin the model are:
1) Fraction of land in turf.
2) Fraction of land which is impervious.
3) Average personsper dwelling
4) Housing density.
5) Precipitation rate.
6) Water rechargedfrom turf.
7) Water rechargedfrom natural land.
8) Evaporation from impervious surface.
9) Runoff from impervious surfacesthat is recharged.
10) Home water use per person.
11) Nitrogen concentrationin precipitation.
12)
concentration
13) Nitrogen
Turf fertilization
rate. in water used.'
14)
15)
16)
17)
18)
Fraction of nitrogen leachedfrom turf.
Fraction of wastewaternitrogen lost as gas.
Wastewaterfraction removedby sewer.
Nitrogen per personin wastewater.
Nitrogen removal rate of natural land.
Each of thesevariables is discussedand model input valuesare defined.
The areasthat were modelledare the sections(termed cuttings) of the
subdivisionsthat are impacting selecteddowngradientmultiport wells. The
monitoring networks were not randomly spacedacrossthe subdivisions;therefore, the
data are more representativeof a part of the subdivisionsthan of the entire
70
subdivision, Becausea goal of the project was to compareBURBS predictions with
field monitoring values, it was necessaryto define the BURBS variables in terms of
the conditions impacting the monitoring network. Thus, while the demographic-type
variables were defined using averagesfor the entire subdivision, the areal-type
variables were basedon specific land use within the cutting areas.
Onsite waste disposalis the primary sourceof nitrogen loading to groundwater
from a subdivision. Once the model variableswere accuratelydefined, simulations
were run to evaluatethe effect of doubling and halving the housing density (hence
septic systemdensity) Relativeamountsof land useareas(i.e., turf, natural,and
impervious) were adjustedto accommodatethe increased(decreased)amount of
imperviousareaassociated
with more(fewer)housesin a givenarea. For these
simulations, the area of housesand driveways were doubled (halved) and the area of
turf and natura11anduse were reduced(increased)by an amount in proportion with
their baselineareas, The amount of road area was kept constant.
A numberof runsweremadeto calibratethe modelin termsof the amountof
nitrogen leachedfrom lawn fertilizers. For thesesimulation runs, the amount of
wastewaterremovedby sewer was set at 1.00, to eliminate wastewaterimpacts from
the simulation results. The leachingvaluesrangedfrom 0.05 to 0.40. The leaching
value consideredto be most representativeof observedin-field conditions was the one
that yielded a nitrate-N concentrationmost similar to the concentrationsmeasuredin
water samplesof wells impactedsolely by lawns (approximately4.3 mg/l nitrate-N)o
Severalruns were madeto demonstratethe effect of precipitation amountson
groundwaternitrate-N concentrations. Wet years and dry years were simulated.
71
Once the model was defined for the sandysoils, severalruns were madeto
demonstratehow soil type and reducedgroundwaterrechargeaffect nitrate-N
concentrationsin groundwater.
Variable Definition
The fraction of land in turf, impervious, and natural ground covers in the
cuttings were calculatedby pc/ARCINFO from the subdivisionmaps. Maps of the
cuttings are shown on Figures 15 and 16. In the simulationswhere the housing
density was varied, the land use percentageswere modified to accountfor the
differing amount of impervious area occupiedby residences. For thesesimulations,
the fraction of impervious area was divided into roads and residences(including
buildings, and driveways). The residentialimpervious area was modified by the
changesin housing density (doubledor halved), but the road area was kept the same.
The fraction of land in turf and natural were modified to accountfor the changein
.
ImpervIous
.
area.
The land use fractions usedin the simulationsare summarizedin
Table 8.
The averagenumber of personsper dwelling was 2.97 for Jordan Acres and 3.53
for Village Green. Thesevalues were determinedby surveyinga portion of the
subdivision occupants. Approximately 50 percent of the homesin Jordan Acres and
35 percent of the homesin Village Green were surveyed
The housing density for each scenariowas calculatedusing the total number of
housesin each area of interest and dividing by the total area of the cutting. The value
for JordanAcreswas3.7 homesper hectare;Village Greenwas2.9 homesper
hectare. Thesevaluesinclude roads, vacantlots, natural areas,and public lands.
72
.
~
0
.-
~
~
0
-
--
~
~
~
=
.~
0
..=
rIJ
~
~
>.
"C
=
't7J
I
..c
=
rIJ
=
0
..~
~
."C
..c
=
rIJ
~
'"
~
-<
=
~
"C
'"
0
~
c.O
Co
~
~
.
~
~
~
'"
~
~
3
r/J
I
t>I
n
cd
Co)
0
. .,
~
/l
1"\
'"I
r:::-
ra.
~
0
-Q.)
.--4
'"I
1'1
-
--:I
~
(1)
n
r-c
A,.
=°'
Q
~
C':J
(1')
O.D
m
.~
>-
...
~..
~
n
M
In
0'1
~
ro
n
~
~
~
.,
roc
~
~
U:J
I
...c
~
rr"
n
"I
~
Un
~
m
~
D
n
~
n
n
n
~
M
<:\
~
-
n
-
M
~..
. -
-
..
II)
N
~
tr)
a
-J
w
H
u.
Z
H
<
0:
a
a
z
<
I
74
~!
,
'"
.
I
'"
C1.)
13::
-
~
-,
~
..
-c
~
Q
...
~
-g
~
=101
d
~
.
.
-'"
...
~
D/"I
(1)
H
-
co;,
1'1
cd
~
C1
~
..
-
d
=
0
~
f;.,
~
/"I
Q,)
0-
~
.
~
11\
'"'d
--
~
~
s
~~
tr)
-J
-J
~
.
.
~
...
L
0
Q.
...
~
~
.
.
:E
U
...
Q.
.
(/)
"U
C
0
C
:1
~
RR
~
=
...
.
3.
.
...
0
>
.
.
~
.
:x
>.
>
.
ItC
11
1::.
AL
L
J
"1
r:;l
Fl ra
~
Q
~
~
~
~
~
'C
=
~
I
"Q
=
(IJ
=
Q
...
.~
>...
'C
"Q
=
(IJ
=
~
~
OJ
~
~
...
;>
c.,.
Q
Q,
~
~
.
I,C
~
~
=
~
...
~
~
r--
Table 8. Relativeamount of turf, natural and imperviousareasin the BURBS
simulation for the Jordan Acresand Village Greencuttings.
The actual lot sizesare approximately0.17 to 0.2 hectares.
The BURBS model considersthe housingdensity to be equivalentto septic
systemdrainfield density It further assumesthat the drainfields are evenly
distributed throughout the subdivision. Observedin-field conditions indicate that
someof the wells potentially get impactedby many drainfields, while others get
impactedby few or none. To simulatethis variability, the drainfield density was
doubled in certain scenariosand halved in other scenarios.
Precipitation data are presentedin Figure 7. The estimatedgroundwatertravel
time beneathJordan Acres rangedfrom 1.6 to 2.9 years; the travel time beneath
Village Green ranged from 4.8 to 9.0 years. The averageprecipitation from the years
1985 through 1990 (78 cm) was usedfor BURBS simulationsmodeling Jordan Acres;
the averageprecipitation from 1981 to 1991 (83 cm) was usedwhen modelling
Village Green
In order to demonstratehow fluctuationsin precipitation can affect groundwater
quality, the precipitation amount from relatively wet years and dry years was usedin
75
~.
~.
~.
Figure 17. Water table elevation measured from the Jordan Acres northwest
survey well, and precipitation measured at the StevensPoint, Wisconsin
wastewater treatment plant from 1987 to 1991.
severalsimulations. The values that were chosenwere the wettestand driest years
over the time spanusedto determineaverageprecipitation amounts(64 and 88 cm for
Jordan Acres; 64 and 114 cm for Village Green).
Water rechargedto the groundwaterfrom turf and natura11andwas assumedto
be equal to the total amount of precipitation minus 53 cm of evapotranspiration.
Additional rechargewas calculatedby the model to accountfor runoff from
imperviousareasto lawnsandnaturalareas. The evaporationfrom impervious
surfaceswas set at 10 percent, as recommendedby the BURBS documentation.
76
The runoff from impervious surfacesgoing to rechargewas not defined with a
great deal of certainty, due to the complexity of influencing factors. For example:
rain that lands on rooftops is diverted to eavestroughs, where it is dischargedto the
ground in specific locations. This additional water will saturatethe soil quicker than
the rain would itself, thus facilitating water movementinto the ground. Water that
runs off from roads to ditches will behavein a similar manner. Water from
impervious surfaceswill be subjectto someevapotranspiration(ET); however, the
localized area receiving the runoff water will quickly becomesaturated,thus
facilitating water movementthrough the vadosezone and into the aquifer. ET is
already included in the 53 cm/year value, the additional runoff mostly goes to
recharge Becausethe soils have a very low water-holdingcapacity (which can
quickly be met by the precipitation event) the additional runoff from impervious
surfacesis available to rechargethe groundwater, No surfacerunoff to storm sewers,
waterways,or streamsoccursin eithersubdivision.For modellingpurposes,it was
assumedthat 90 percent of the water not evaporatingfrom impervious areasgoes to
groundwaterrecharge. Becausethis rechargewater will have low nitrate-N levels, it
will tend to lower averagenitrate-N concentrations(by dilution) but not significantly
effect nitrogen loading This additional rechargein areaswith sandysoil helps keep
nitrate-Nlevelsin the rechargewaterlow, comparedto areasof heaviersoil, where
water will runoff and not aid in diluting the effects of septic systems,
The volume of water usedper personin the subdivisionswas estimatedafter
consideringseveralsources The US EnvironmentalProtection Agency estimatesthat
the per capita rate of water use is 70 liters per personper day (USEPA, 1980). We
77
conducteda survey to determinehome water use in the city of StevensPoint, which
indicateswater consumptionof 270 liters/person/day. This estimatemay be high
becauseof the uncertaintyof the actual numberof personsper household(assumedto
be 3). Also, it has been suggestedthat homeownerswith septic systemsare more
consciousof their water use than thoseon city water and thus tend to be more
conservativein terms of water use. A water meter was installed on the well at a
residencein the Jordan Acres subdivision. The two adult occupantseach used
approximately 190 liters of water per day over a twelve month period Data obtained
from an investigationmonitoring 15 septic systemsin nearby rural homesindicate that
home water use is closer to 130 liters per personper day (Shawand Turyk, 1992). A
value of 150 liters/person/daywas usedin the simulations.
The EnvironmentalTask Force Lab - UW StevensPoint testedfor the nitrogen
concentrationin precipitation frequently throughoutthe 1980s(unpublisheddata).
The averagenitrate-N concentrationdeterminedby this study was 0.25 mg/l.
Privatewell datafrom manyof the homesin the subdivisionwereusedto
calculatean averagenitrate-N concentrationin the water usedin the subdivisions.
The averagefor Jordan Acres was found to be 6.9 mg/l and the averagefor Village
Green was 11.3 mg/!.
The turf fertilization rate used in the model simulation was based on data
obtainedby the survey of subdivisionhomeowners(SectionD). The survey results
indicated that 74 percent of all respondents used the amount specified by the
manufacturer, 18 percent used more than was specified, 6 percent usedno fertilizers,
and 1 percent did not read the bag
78
The survey also revealedthat the overall
fertilizer application rate was 1.6 times per year (1.8 times for users). A value of
0.78 kg/IOO m2 was used in modelling both subdivisions (assuming a 0.49 kg/IOO m2
rate applied .6 times per year).
Petrovic's (1990) review of relevant researchrevealedthat although the amount
of nitrogen leachedfrom fertilized turf grasswas highly variable, it was generally less
than 5 percent that was leachedto groundwater. The exceptionswere in areaswhere
the fertilizers were applied in excessiveamountsand/or the turf was over watered.
The BURBS variable definitions cite a Long Island study that indicated up to 50
percent of lawn fertilizers usedin sandysoils leachedto groundwater. Becausefield
data from lawn impactedgroundwaterwas available, the value for this variable was
defined using a range of values, then comparingthe results with the field data. The
leaching value that yielded the most representativeresults was used for the baseline
value in the model. For calibrating purposesit was assumedthat all of the nitrogen
in wastewaterwas removedby sewers,
Studieshave shown that in well aeratedsandysoils, the amount of nitrogen in
wastewaterlost as a gas is negligible (Walker, et aI, 1973). This conclusionwas
supportedby studiesof private waste disposalsystemsin a nearby subdivision (Shaw
and Turyk, 1992). The value of 0 was usedfor this variable.
The subdivisionsare unsewered,thus the wastewaterfraction removedby sewer
was set at 0 (exceptwhen usedto calibrate the fertilizer leaching variable as discussed
above),
The amount of nitrogen per personin wastewaterhas been fairly well
documented. A value of 4.5 kg/person/yearwas reported by Walker et.al. (1973).
79
This value was also found for 15 septic systemsin the StevensPoint area (Shawand
Turyk, 1992). Samplesfrom a septic tank serving two adults in Jordan Acres
contained60 and 89 mg/l of total Kjeldahl nitrogen in the wastewater. The daily.
water use by this householdwas measuredto be 190 liters/person/day,thus the annual
nitrogen loading rate is estimatedto be 4.4 to 6.4 kg/person/year. A value of 4.5
kg/person/yearwas used for modelling purposes.
The nitrogen removal rate of natural land was set at 0.9 as recommendedby
BURBS documentation,but it is negligible in model simulationsbecauseof the low
nitrogen concentrationin precipitation. Values for the variables usedin the BURBS
simulationsare summarizedin Table 9.
AO
Variable
Jordan
Acres
Village
Green
Fraction of land in turf-baseline
0.66 *
0.41 *
Low upgradientdrainfield density
0.72
0.45
High upgradientdrainfield density
0.55
0.33
0.22*
0.24 *
Low
0.16
0.17
High
0.35
0.39
Average personsper dwelling
2.97*
3.53*
Housing density (#/hectare)
3.7 *
2.9 *
Low upgradientdrainfield density
1.8
1.4
High upgradientdrainfield density
7.4
5.7
78 *
84 *
Dry year
64
64
Wet year
88
114
Fraction of land that is impervious-baseline
Precipitation rate (cm/year)
Water rechargedfrom turf (cm/year)
Precipitation-53
Water rechargedfrom natural land (cm/year)
Precipitation-53
Evaporation from impervious surface(fraction)
0.1*
0.1 *
Runoff from impervious recharged(fraction)
0.9 *
0.9 *
Home water use per person (liters/day)
151 *
151*
Nitrogen concentrationin precipitation (mg/l)
0.25 *
0.25 *
Nitrogen concentrationin water used(mg/l)
6.9 *
11.3*
Turf fertilization rate (kg/IOOm2)
0.78*
0.78 *
Fraction of nitrogen leachedfrom turf (fraction)
Varied from 0.05 to 0.40
0.25 *
0.25 *
Fraction of wastewaterN lost as gas (fraction)
0*
0*
Wastewaterfraction removedby sewer(fraction)
0 **
0 **
Nitrogen per personin wastewater(kg/year)
4.5 *
4.5 *
Nitrogen removal rate of natural land (fraction)
0.9 *
0.9 *
* Used for baselinemodel run
** 100 % usedwhen calibrating fertilizer leaching
Table 9. Valuesfor the variablesusedin the BURBSsimulationfor Jordan
Acres and Village Green.
81
Simulation Results
The results of the various BURBS simulationsare presentedin Table 10 and
Appendix B
The fertilizer leaching estimatesfor Village Green are 30 to 35 percent lower
than those for Jordan Acres. This is becauseJordan Acres has a higher percentageof
its land use as turf, whereasVillage Green has more natural and impervious areas.
The non-turf or natural areashave a diluting influence on the nitrate-N concentrations.
Resultsof the Jordan Acres BURBS simulationsthat comparefertilizer leaching
rates were evaluatedto determinethe amountof leachingoccurring within the
subdivisions. Becausethe averagenitrate-N concentrationof wells monitoring lawn
areaswas 4.3 mg/l, the leaching rate for the baselinevalue usedin the simulations
was set at 25 percent. Jordan Acres results were usedbecausemost of the wells used
to monitor lawn impacts were in that subdivision. The 4.3 mg/l nitrate-N is also
close to averagefor the Village of Park Ridge, a seweredvillage adjacentto Stevens
Point with all groundwaterrechargeoriginating from the urban area (ETF
unpublisheddata).
For Jordan Acres, the 25 percentleaching rate accountsfor about 21 percent of
the total nitrogen budget, as comparedwith the results of the baselinesimulation; for
Village Green the 25 percentrate accountsfor 18 percent. Varying the leaching rate
by five or even ten percent either up or down has little significant impact on overall
nitrate-N concentrations,thus the 25 percentleachingrate is consideredto be
appropriate.
82
Study area and simulation
conditions
Average NOJ in
Recharge
Nitrogen Leached
Water
Recharged
mg/l
kg/Ha
BaselineVariable Values
17.2
67.3
60.1
39.1
15.4
High Upgradient Drainfield Density
23.7
119
106
48.3
19.8
12.3
41.4
37.0
33.5
13.2
Wet Year (88 cm of Precipitation)
13.8
67.4
60.2
49.0
19.3
Dry Year (64 cm of Precipitation)
26.1
67.2
60.0
25.7
10.1
0.9
3.0
2.7
33.0
13.0
1.7
5.7
5.1
33.0
13.0
3.3
11.0
9.8
33.0
13.0
fertilizer leaches
4.1
13.6
12.1
33.0
13.0
- 30%
of fertilizer leaches
4.9
16.2
14.5
33.0
13.0
- 40%
of fertilizer leaches
6.5
21.5
19.2
33.0
13.0
13.7
60.9
54.4
44.5
17.5
QQ R
~~ Ii
21.9
Ib/acre/yr
cm/year
inch/year
Jordan Acres Cutting
(7.4 dwellings/hectare)
Low Upgradient Drainfield Density
(1.8 dwellings/hectare)
No Drainfield Impacts and:
- 5 % of
fertilizer .leaches
- 10% of
fertilizer leaches
20% of fertilizer leaches
- 25 % of
Village
Green
Cutting
BaselineVariable Values
(5.7 dwellings/hectare)
HighUpgradientDrainfieldDensity
II?
20.0
---
Low UpgradientDrainfield Density
(1.4 dwellings/hectare)
9.1
35.5
31.7
38.8
15.3
Wet Year (114 cm of Precipitation)
8.3
61.2
54.6
73.9
29.1
Dry Year (64 cm of Precipitation)
23.2
60.7
54.2
26.2
10.3
-5 % of fertilizer leaches
0.6
2.1
1.9
38.9
15.3
- 10% of fertilizer leaches
1.0
3.8
3.4
38.9
15.3
-20% of fertilizerleaches
1.8
7.1
6.3
38.9
15.3
-25% of fertilizer leaches
2.2
8.7
7.8
38.9
15.3
- 30% of fertilizer leaches
2.7
10.4
9.3
38.9
15.3
,. - 40% of fertilizer leaches
3.5
13.7
12.2
38.9
15.3
No Drainfield Impactsand:
!
I
-,
Table 10. BURBS simulation results for the Jordan Acres and Village Green
cuttings.
83
The results of varying the drainfield density, in addition to the results from
simulationsthat assumedno drainfield impacts, supportsthe observationsand
conclusionof severalother authors (Yates, 1985 and Perkins,1984) that septic sY05tem
drainfields are the primary causeof elevatednitrate-N concentrationsin the
groundwaterbeneathunseweredsubdivisions. Note that in Jordan Acres, even at a
relatively low drainfield density (1.9 dwellings/hectare)BURBS predicts nitrate-N
concentrationsin excessof the enforcementstandardfor nitrate-N of 10 mg/!. In
Village Green, the low drainfield density simulation yielded a result below the 10
mg/! standard. The area for this simulation was one home for every 0.7 hectares. It
should be noted that the rechargerate of 29.7 cm used for Village Green is much
higher than the 25.4 cm long term averagefor the area. Simulationswere run to
determinethe housing density that would be neededin Village Green and Jordan
Acres to achievea 10 mg/l nitrate-N concentrationin recharge. Thesehousing
densitiesare 1.7 dwellings/hectarein Village Green and 1.1 dwellings/hectarein
Jordan Acres.
Figure 18 showsthe relationshipbetweenhousingdensity and simulated
nitrate-N concentrationsin groundwaterrechargefor Jordan Acres and Village Green
subdivisions. The primary reasonfor the differencesbetweenthe two subdivisionsis
that the precipitation amountsusedfor the two subdivisionsdiffered by 5. cm which
resultedin less recharge,and therefore less dilution in Jordan Acres simulations, The
higher percent of the area in lawns in Jordan Acres resultedin more fertilizer
leaching which was largely offset by a slightly higher number of people per household
in Village Greens,which increasesnitrate-N leaching.
84
.Jor-dan Acr-es and Vi Ilage
Gr-een Cuttings
Housing Density
BURBS Simulations
26
24
--
22
E>
20
r\
~
\.J
18
16
Z 14
I
12
QI
...
10
13
L
...
Z
8
6
"'"
4
2
3
!-busing
4
Denslt:y
Jordan
Acres
e
5
L6
(housing/hect:are)
VI
I laoe
Green
*
Figure 18. BURBS estimated nitrate-N concentrations related to varying housing
densities at Jordan Acres and Village Green subdivisions.
Jordan Acres is the simulation that best representsthe sandy soil areasof
Wisconsin, as the precipitation data usedis closestto the long term averagefor
Wisconsin and the number of peopleper home (2.97) is close to the stateper
householdaverage.
Precipitation amountscan also greatly affect groundwaternitrogen
concentrations. In wet years, there will tend to be more water available to dilute the
nitrogen input from septic systems;in dry years, less dilution will occur and nitrate-N
concentrationswill be higher. Table 10 presentsresults of simulationsfor Jordan
Acres and Village Green, where precipitation extremesduring the study period for
each subdivision were used. The range of 64 to 114 cm used for Village Green fives
simulatednitrate-N concentrationsof 23.2 to 8.3 mg/!, where only this variable was
85
changed. Precipitation extremesmay have a short-termimpact on groundwater
quality and accountfor someof the variability found in shallow wells. Precipitation
extremescan have a dramatic effect on groundwaterquality if the conditions persist
for severalyears.
Simulation for Heavier Textured Soils
In addition to the simulationsrun for Village Green and Jordan Acres, several
runs were madechangingthe routing of runoff water and reducing groundwater
rechargeto 10 cm/year, which is consideredto be a reasonableestimateof the
statewideaveragefor groundwaterrecharge. Thesesimulationsare presentedin
Figure 19. The simulationsare consideredto be indicative of what one would expect
in areasof heavier textured soils and/or greater slope. The Village Green set of
valueswere used for the variablesexcept for the reduction of rechargefrom natural
areasfrom 30.0 cm (11.8 in) to 10.2 cm (4.00 in), and rechargefrom runoff from 90
percent to 12 percent. The fraction of fertilizer that leachesfrom fine-textured soils
tendsto be less than in sandysoils (Petrovic, 1990), therefore, the value for this
variable was reducedfrom 0.25 to 0.05 This resultedin nitrate-N concentrationsof
34.9 mg/l, comparedto 13.7 mg/l for the Village Green baselinevalues. Lot size to
achievea nitrate-N concentrationof 10 mg/l increasedfrom 0.6 hectares/dwellingto
2.0 hectares/dwelling,
Theseruns of the model indicate the importanceof having good estimatesof the
~mountof groundwaterrechargethat will occur from lawns, natural areas,and also
that due to runoff from impervious areas. This variable is of equal importanceto
housing density when using a massbalancemodel,
AI;
v
age Green Cutting
BURBs Simulattons
-
Housino
Heavier
So s
Density
"
~
u
Z
I
Q)
...
10
L
...
Z
Figure 19. BURBS estimated nitrate-N concentrations related to varying housing
densities in heavy soils using Village Green subdivision variables.
Subdivisiondesignsthat maximize local groundwaterrechargewill provide
maximum dilution of nitrogen inputs from septic systems. These scenariosalso
indicate that fertilizer leaching in sandysoil areas,while a significant part of the
nitrogen budget, is effectively diluted by high rechargeamounts Decreasedrecharge
with a similar percentof fertilizer leaching results in much higher nitrate-N
concentrations reaching groundwater from lawns, More researchis neededto
evaluatenitrogen lossesfrom lawns on different soil types in Wisconsin,
Overall, we believe the BURBS program provides a fairly accurateestimateof
nitrogen inputs from subdivisions. Someof the variables (discussedpreviously) need
careful evaluationfor accurateapplicationof the model. It must be recognizedthat
87
the model predicts averagenitrogen concentrationsin the entire subdivision recharge.
would be needed,and no mixing with upgradientgroundwatercould occur. This is
wells from intercepting contaminantplumes is neededif current waste disposal
practicesare to be used.
88
F. Nitrogen and Water BudgetResultsfrom Field Data
The variables and results of nitrogen and water budgetsusing subdivision field
data are presentedin Table 11.
The area values usedin the budget calculations(width of cross sectionand
length of flow path) were basedon data obtainedfrom only a portion of the
subdivisions(termed cuttings). The area included in the Jordan Acres cutting is
shown on Figure 15; the Village Green cutting is shown on Figure 16 (pages73 and
74).
The depth of subdivisionimpactedwater was estimatedbasedon the chemistry
data obtainedfrom the downgradientmultiport wells that are discussedin SectionH.
The averagelinear groundwaterflow velocities were determinedbasedon a
range in hydraulic conductivity from 0.045 cm/sec to 0.085 cm/sec for both
subdivisions,an effective porosity of 0.30, and hydraulic gradientsof 0.0026 (Jordan
Acres)and0.0020(VillageGreen). The dischargevolumeswerecalculatedbasedon
thesehydrogeologiccharacteristicsand the cross-sectionalarea impactedby the
subdivision.
The averagenitrate-N concentrationswere calculatedfrom thoseports at the
downgradientmultiport wells that were determinedto be monitoring the groundwater
rechargedfrom subdivision sources,as discussedin SectionH
The massof nitrogen dischargedfrom the cuttings was calculatedusing the
averagenitrate-N concentrationsand the volume of discharge(mg/l x m3/yearx 0.001
kg/year),
The groundwaterflow times acrossthe cuttings were calculatedusing the
89
Characteristic
Jordan
Acres
Cutting
Village
Green
Cutting
Width of cross section (m)
180
180
Length of flow path along cutting (m)
360
850
Depth of subdivision impactedwater (m)
3.4
7.7
Area of cross sectiondischarginggroundwaterfrom the cutting (m~
612
1400
0.34
0.26
0.49
0.37
0.64
0.49
23,000
39,000
Dischargeof subdivision impactedgroundwaterfrom cutting medium (m3/year)
33,000
57,000
Dischargeof subdivision impactedgroundwaterfrom cutting - high
43,000
74,000
9.0
13.6
Mass of nitrogen in dischargefrom cutting low (kg/year)
200
530
Mass of nitrogen in dischargefrom cutting - medium (kg/year)
300
770
Mass of nitrogen in dischargefrom cutting - high (kg/year)
390
1010
2.9
9.0
2.0
6.3
Groundwaterflow time acrosscutting - fast (years)
1.5
4.8
Average yearly precipitation (cm)
78
83
16,000
46,000
Average linear groundwaterflow velocity - medium (m/day)
Average linear groundwaterflow velocity low (m/day)
Average linear groundwaterflow velocity - high (m/day)
Dischargeof subdivision impactedgroundwaterfrom cutting - low
(m3/year)
(m3/year)
Average nitrate-N concentrationof groundwaterleaving cutting
(mg/l)
-
Groundwaterflow time acrosscutting - medium (years)
Groundwater flow time acrosscutting slow (years)
Volume of water rechargedassumingno drainfields, no impervious
areas,and recharge = annualprecipitation - 53 cm (m3/year)
Table 11. Results of nitrogen and water budget calculations based on field data
obtained from Jordan Acres and Village Green subdivisions.
90
length of the subdivisionand the range in averagelinear groundwaterflow velocities
(metersx days/meterx 1/365 = years).
The averageannualprecipitation was calculatedbasedon the average
precipitation that occurred over the groundwaterflow time beneaththe subdivision
during the study period (JordanAcres, 1986 to 1990; Village Green, 1981 to 1990).
The estimatedvolume of water that would rechargethe aquifer under natural
conditions (i.e., if there were no humanimpacts)is estimatedby using precipitation
minus 53.3 cm evapotranspiration. This volume is included to demonstratethe
increasein rechargethat occurs in subdivisionson sandy soils. The volume of
rechargefrom a subdivisionis expectedto be greater than the amount from an equal
area of natural land becausemore of the water that falls on impervious surfaces(90
percent of precipitation) will rechargeto the groundwater,as comparedwith about 25
percent from vegetatedareas. This is discussedin greater detail in SectionE.
91
G. Comparisonof the Resultsof the Nitrogen and Water BudgetsDetermined
by Two SeparateMethods
The nitrogen and water budgetresults determinedusing the BURBS computer
program and the results basedon field data are presentedin Table 12. Three field
data scenariosare presentedfor comparisonpurposeswith the BURBS baseline
results.
There is very good agreementbetweenthe two methodsfor the Village Green
subdivision, both nitrogen loss and water budget calculationsare in agreementfor the
medium to high groundwaterflow velocity values. We feel this validatesthe results
of the BURBS model, Resultsfrom the Jordan Acres subdivisiondo not agreeas
Budget Results
Average Nitrogen
NO3in
Leached
Recharge (kg/yr)
(mg/l)
Water
Recharges
(m3/yr)
Jordan Acres
BURBS: Baselinevalues
17.2
440
25,000
Field data: Low hydraulic conductivity
9.0
210
23,000
Field data: Medium hydraulic conductivity
9.0
300
33,000
Field data: High hydraulic conductivity
9.0
390
43,000
Water rechargedassumingno impervious areas
16,000
Village Green
BURBS: Baselinevalues
13.7
930
68,000
Field data: Low hydraulic conductivity
13
530
39,000
Field data: Medium hydraulic conductivity
13
770
57,000
Field data: High hydraulic conductivity
13
1000
74,000
Water rechargedassumingno imperviousareas
46,000
Table 12. Nitrogen and water budget results for Jordan Acres and Village Green
cuttings. Results were calculated using both the BURBS computer program and
actual field data.
92
well. If we use the low hydraulic conductivity value, the water budget for the
methodsgenerally agree (Table 12), however, the estimatednitrogen loss (210 kg)
would only be about half of that predictedby the BURBS model (440 kg), The
primary reasonfor the discrepancyin this subdivisionis the high nitrate-N
concentrationspredictedby BURBS (17.2 mg/l), comparedto that observedfrom the
six downgradientmultilevel wells (9 mg/l).
We have no reasonto suspectany nitrogen loss by denitrification in the Jordan
Acres soils or aquifer and believe the nitrate-N discrepancybetweenpredictedvalues
and multilevel wells is due to the groundwaterchemistry data obtainedfrom the
monitoring network not being truly representativeof overall subdivisionimpacts.
The extreme variability of nitrate-N in monitoring wells downgradientof this
subdivision, ranging from 1 to 50 mg/l, (Figure 36, page 114) clearly indicatesa
wide range of water quality values downgradientof this subdivision as comparedto
Village Green. At Village Green the well placementwas much easierdue to the
accessibilityof a vacant field downgradientof the subdivisionand becausethe
groundwaterflow is generally parallel to the subdivisionlayout. At Jordan Acres the
monitoring wells were placed where homeownerswould permit their installation,
Therefore we are not confident that even this large number of multilevel wells is
providing a representativesampleof groundwaterat the Jordan Acres site. We feel
that the results of the BURBS simulationsare more representativeof actual recharge
characteristicsthan the data obtainedfrom the monitoring wells.
93
H. GroundwaterQuality Downgradientof Subdivisions
A number of multilevel wells were installed downgradientof each subdivision to
determinesubdivisionimpact on groundwaterquality, determinethe variability of
water chemistry horizontally and vertically downgradientof the subdivision, and to
determinechangesin water chemistry over time,
Figures 3 and 4 (pages33 and 34) show the location of downgradientwells used
for this part of the project. Initially (in 1987), there were only two multilevel wells
installed downgradientof each subdivision; E4 and W4 in Jordan Acres, and S4 and
N4 in Village Green. Data from thesewells was not consideredto be sufficient to
evaluatesubdivisionimpact on groundwater. Additional multilevel wells were
installed in 1989 to determinethe variability of groundwaterchemistry downgradient
of the subdivisions,to provide better quantitativeestimatesof water chemistry leaving
the subdivisions,and to aid in making recommendationson future well designsfor
subdivisionevaluations.
Comparing upgradientwater chemistry with downgradientconcentrationscan be
very misleading. The shallowestdowngradientwell ports are samplingwater
rechargedonly from the subdivision. Mid-depth wells are believed to be sampling a
mixture of water rechargedfrom upgradientof the subdivisionand that originating
from within the subdivision, while deeperwell ports are samplingwater originating
only in upgradientareas. Changesin water chemistry with depth were very useful in
identifying the parts of the aquifer impactedby rechargefrom different land uses,
The monitoring well systeminstalled in Village Green turned out to be easier to
94
quantitatively evaluatethan that for Jordan Acres, however, both show good
relationshipsbetweenwater quality, well depth, and land use.
The depth of groundwaterimpactedby the subdivisionis important in calculating
the extent of subdivisionimpact and also to validate the nitrogen massbalancemodel
This depth can be estimatedusing water chemistry graphsof multilevel well data.
For the Village Green subdivision(which had a saltedfour lane highway separating
the subdivision from an intensively managedagricultural field upgradientof the
subdivision) the relative amountsof chloride and sodium proved to be most useful.
Figure 20 presentsthe chloride to sodium ratio and Figures 21 and 22 show the
chloride and sodium graphsfor the samewells. In general, the upgradientwater
chemistry in Village Green has very high chloride to sodium ratios due to large
chloride impacts from agricultural fertilization with low inputs of sodium. Recharge
from the highway and from septic systemswill increasethe concentrationsof both
chloride and sodium, thereby reducing the chloride to sodium ratio.
Figures 23 and 24 show fairly high concentrationsof relative fluorescenceand
phosphorousin the shallower depthsof the aquifer from Village Green subdivision.
Thesechemicals,however,do not movethroughthe aquiferas easilyas nitrate-Nor
chloride, and are usedprimarily to verify the presenceof subdivisionimpacts.
From thesegraphs, we estimatethe upper 4.7 metersof the aquifer are
composedof subdivisionoriginated water, with the 4.7 to 12 meter depth being a
mixture of subdivisionrechargeand that from upgradientof the subdivision If we
assumedthis was a 40:60 mixture of the two, the amount of subdivision recharge
would be 4.7 metersplus 40 percentof the 4.7 to 12 meter depth, for a total of 7.6
q~
metersof subdivision originated water. The volume of water representedby this
effective aquifer thicknesscomparesfavorably with the estimateof subdivision
rechargefrom the BURBS model, discussedearlier in this report (SectionE).
330
325
-c
0
",p
It!
>
OJ
W
.J
~
~
320
315
310
0
2
4
Chloride
~
~4
8
6
to Sodium
~3..5J
10
Ratio
~~l2 ~i~1
Figure 20. Average chloride to sodium ratios with depth in groundwater from
downgradient wells at Village Green.
96
. Figure 21. Average chloride concentrations with depth in groundwater from
downgradient wells at Village Green.
330
325
c
0
O;; 320
m
>
Q)
w
~
cn
~
315
310
0
10
20
30
Sodium
~~~..s:.
40
50
60
(mg/l)
~~L2~t~1
Figure 22. Average sodium concentrations with depth in groundwater from
downgradient wells at Village Green.
97
330
325
-;;;
0Q)
+"'
Q)
E
c
0
°;;
320
CO
>
Q)
W
.J
U)
~
315
310
0
6
15
.-
10
20
:,-_,
RelativeFluorescence
N4 WAL4 WAL3 54 WAL2 WAL1
-eFigure
23.
Average
Village
Green.
330
relative
~
-e-
...e...
fluorescence
..;A:--
with
depth
in downgradient
wells
at
325
"Ui'
OJ
...
OJ
.£
c:
0
.~ 320
co
>
OJ
W
-J
U)
~
315
310
0
0.05
0.1
Phosphate
0.15
0.2
0.25
(mg/l)
~ ~ ~.. 5J.~~l2 ~t~1
Figure 24. A verage phosphate concentrations with depth in downgradient wells
at Village Green.
98
Due to different upgradientland usesat Jordan Acres, sodium to chloride ratios
were not as useful. Nitrate-N, chloride, fluorescence,and phosphorousdata are
presentedas Figures 25, 26, 27, and 28 All show similar results and ind,icatedepths
of impact of 1.3 metersprimarily from subdivisionrecharge; 1.3 metersto 9.5 meters
into the aquifer for the mixed zone, and water below 9.5 meterspredominantly from
upgradientrecharge.Apparently,thereis somelocalizedmixing downto 9.5 meters
into the aquifer under this subdivision, while other areasshow minimal mixing as
evidencedby shallow concentratedplumes over 30 metersdowngradientof
drainfields. To estimatethe volumeof subdivisionimpactedwater,we usedthe upper
1.3 meter depthsplus one quarter of the next 8.2 metersfor a total of 3.4 meters.
We used the averagenitrate-N concentrationsof the upper 1.3 metersto estimatethe
amount of nitrogen leaving the subdivisionas discussedin the previous section
Comparisonsof thesevalues to BURBS predictionsare discussedin section G.
99
335
Top of Aquifer
~...
Top of Mixing Zone
, ~.
330
""iii
...
Il>
+"'
Il>
'~
""'"
I.
.§.
c:
0
"+"' 325
10
>
Bottom of Mixing Zone
Il>
W
~
cn
~
/
320
/)
,I
-/'
315
Top of Aquifer
~ ~.
::-~
330
Top of Mixing Zone
-;;;
Q;
...
111
E
c
0
~
co
325
>
111
W
~
cn
~
320
Bottom of Mixing Zone
'/
.
316
0
10
20
30
Chloride (mg/l)
40
50
-
60
~~~
.~f i ~ ~-_.
Figure 26. Average chloride concentrations with depth in downgradient wells at
Jordan Acres.
100
335
1114'"
---'
330
Iii
Q;
+-'
III
Top of Mixing Zone
~~
.s
c
0
°+:i 325
./f1~
tU
>
III
Bottom of Mixing Zone
W
.J
U)
~
320
'-"
315
0
"
l
10
15
25
--
20
~n
~-
Relative Fluorescence
~~~
.~f i
~
~...
Figure 27. A verage relative Fluorescencewith depth in downgradient wells at
Jordan Acres.
335
I
330
""iii
'a>
+"'
OJ
.5
c
0
.~
>
OJ
W
325
~
cn
~
320
316
0
0.02
0.04
0.06
0.08
Phosphate
(mg/l)
0.1
0.12
0.14
~~~.~l
i ~ ~...
Figure 28. A verage phosphate concentrations with depth in downgradient wells
at Jordan Acres.
101
I. hnpact of Lawns on GroundwaterQuality
Severalof the monitoring wells installed throughoutthe subdivisionswere
designedto monitor groundwaterrechargedfrom lawn areasand were not
significantly impactedby septic systems. Data for five of thesewells are presentedin
Table 13, The well that showedthe greatestgroundwaterimpact (MCD LD) was
downgradientof a lawn that received four fertilizer applicationsper year. Chemistry
data for all sampling dates from the upgradient and downgradient wells monitoring
this lawn are presentedin Table 14 and Figure 29.
Well
Location
Well
Point
# of
Samples
Monitoring
Period
NOJ
(mg/l)
CL
(mg/l)
NA
(mg/l)
PO4
(mg/l)
FIR
SD
11
July '88 - Jan '90
4.0
13.3
5.1
<0.002
MCD
LD
12
June '88 - Aug '90
7.8
14.3
5.1
<0.002
£2
22
8
Sep '87 - Aug '89
2.9
4.8
3.9
0.011
E3
25
14
July '87 - May '90
2.7
19.3
12.1
<0.002
S3
22
12
Sep '87 - Mar '89
5.3
37.8
14.7
<0.002
4.5
17.9
8.2
0.001
Average
Table 13. A verage groundwater chemistry data from wells primarily impacted
by lawns.
The upgradientwell was consistentlylow in nitrate-N (less than 1 mg/l) ,
while the downgradientwell fluctuatedfrom 1 to 14 mg/l, with an averageof 7.8
There appearsto be a seasonalityto this data, with the highestconcentrations
foundin summerandfall, andlowestconcentrations
in winter andearly spring. This
pattern would be consistentwith the time of year the fertilizer is applied. Winter
sampling occurred when no recent rechargehad occurred from the lawn area, and
sampleswould representchemistry more characteristicof upgradientland use.
Early spring samplescorrespondto spring rechargeevents, when a lack of large
amountsof residual nitrate-N combinedwith larger volumes of rechargeproduced
reducednitrate-N concentrations. It is widely believed that little residual nitrate-N
remainsin sandy soils over winter due to removal of most of the nitrate-N during fall
leaching.
REE-LU
Sample
MCD-LD
Date
NO3
CI
Na
NO3
CI
Na
06/30/88
0.5
7
2.0
1.0
6
2.0
08/05/88
0.5
6
0.8
3.5
9
2.3
10/20/88
0.8
7
1.5
9.8
13
3.0
01/18/89
0.8
5
2.5
7.8
16
5.5
03/31/89
1.0
7
5.8
9
3.0
OS/26/89
1.2
6
1.6
2.2
10
4.1
08/08/89
1.5
3
1.0
9.8
23
2.0
09/08/89
0.8
5
1.5
14.4
30
11.5
10/26/89
1.2
<1
1.5
13.0
27
7.0
01/08/90
1.0
3
1.5
14.2
11
8.5
02/14/90
0.5
3
1.4
4.8
8
6.9
05/17/90
<0.2
4
1.6
7.0
9
4.8
Count
12
12
12
12
12
12
Average
0.83
5
5
7.8
14
5
Std.Dev.
0.354
2.2
0.43
4.37
7.7
2.84
Table 14. Chemistrydata from two wellsmonitoring the groundwater
upgradient (REE-LU) and downgradient(MCD-LD) of an intensivelymanaged
lawn in Jordan Acres.
1n1
Thesepatternsindicate that fall fertilization on sandysoils should not be done with
fertilizers containing nitrate-NoIf fall fertilization is practiced the residentsshould use
slow releasefertilizer applied late in the year to prevent its convergenceto nitrat~-N.
The meanvalue of 4.5 mg/l nitrate-N for the five sites (Table 13) is consistentwith
private well data from the Village of Park Ridge, a nearby municipality; which is on
public sewerandhasprivatewells. Thesedata were usedin the massbalance
calculationsfor the subdivisions,as discussedearlier.
Jordan
1-8-
Acres
REE-LV
Lawn Nitrate
-
..cO-LO
I
Figure 29. Plot of groundwater nitrate-N concentrations vs time for wells REELU and MCD-LD in Jordan Acres. REE-LU well is upgradient of a lawn, MCDLD is downgradient of the lawn.
104
J. Septic SystemResearch Site Results
Severalsites were instrumentedwith monitoring wells designedto determinethe
impact of septic systemson groundwaterquality. Many of thesewere also used for
evaluationof the trace organic chemicalimpacts (describedin section 0).
Of the ten sites chosenfor the septic systemmonitoring, only five turned out to
generateuseful data. The monitoring wells at the other sites apparentlymissedthe
contaminantplume or only sampledit seasonally. One of the sites (REE) was further
investigatedto determinethe location and size of the plume, and its dispersalwith
distancedowngradientof the drainfield.
Average water chemistry data for the wells that were found to be in at least part
of the contaminant
plumeare presented
in Table 15 A andB. Resultsfrom
correspondingupgradientwells are also shownin thesetables.
At sites MCD, ZAK, and ENG, the downgradientwells were apparentlynear
the edgeof plume, as indicated by the variable results (Appendix A). The two wells
at site KOP were originally intendedto samplelawn impacts, however, they appearto
be impactedby an upgradientdrainfield. Wells at sitesFIR andLaD missthe plume
entirely. Site locationsare shown in Figures 3 and 4 (pages33 and 34)
The original wells at site REE also appearedto totally miss the plume, however,
additional wells installed at this site locatedand tracked the contaminantplume from
this septic system. The results from sites where the contaminantplume was
intersectedand monitored are presentedin Table 15 A. Someof the wells appeared
to be located near the edgeof the plume, as evidencedby the wide fluctuationsin
chemistry results (Figure 15 B). As shownon Tables 15 A and B, the distance
105
betweenthe drainfield and the monitoring wells also varied, which may accountfor
someof the observedvariability,
Resultsfrom wells at Sites REE, AMD, BAR, MaR, and S1 are believed to be
most representativeof shallow groundwaterwithin 6.6 metersdowngradientof the
15 A. Wells consistently monitoring the contaminant plume.
wen
Location
Well
I.D.
# of
Samples
REE
SU
REC
Na
(mg/l)
NO3-N
(mgll)
CI(mg/l)
12
0.7
3
1.3
<0.002
5
Upgradient
SDS
11
48.4
36.2
19.8
<0.002
30
1.5
AMD
su
9
2.9
44
12
0.004
7
Upgradient
AMD
so
9
33.7
133
108
7.0
35
3
BAR
SDA
9
30.9
69
69
6.5
125
8
KEP
MED
8
40.9
85
13
5.03
74
29
MaR
7
5.6
22
16.5
<0.002
16
MaR
su
so
7
19.2
51
41
3.5
31
3.2
ENG
SUA
9
8.5
80
48.6
<0.002
11
Upgradient
LIP
25
6
32
43
54
0.052
21
25
VSl
22
15
24
78
54
0.452
36.4
16
P04
Fluorescence
(mg/l)
Distance from
Drainfield (m)
Upgradient
15 B. Wells occasionallymonitoring the contaminantplume.
Well
Location
wen
1.0.
# of
Samples
ENG
SUA
9
8.5
52
22
13
ENG
SDC
FIR
NO3-N
CI(mg/l)
Na
(mg/l)
(mg/l)
80
48.6
<0.002
16.4
22
13
0.004
10
10.9
65
42
<0.002
12
16
10
3.7
23
0.001
7
Upgradient
MCD
su
so
11
14.1
32
196
<0.002
18
13.3
ZAK
so
9
11.8
20
14
<0.002
14
7.5
(mg/l)
7.6
P04
fluorescence
11
4.9
Distance from
Drainfield (m)
Upgradient
20
Table 15. Average groundwater chemistry of wells in contaminant plumes
originating from nearby septic systems.
106
drainfield. Wells at sites REE, AMD, BAR, and MaR were installed specifically to
monitor the drainfield and were apparentlylocatednear the middle of the contaminant
plume. The 7.2 meter well at 81 also did a good job of samplingthe contaminant
plume from an upgradientseptic system,as did the LIP 8.2 meter well in Jordan
Acres Subdivision.
Some wells showedconsiderablevariability betweensampledates, indicating
they were near the edgeof a contaminantplume. This suggeststhat the plumes
apparentlymove horizontally and vertically on a seasonalbasis as shown in the plot
of groundwaternitrate-N concentrationsover time for severalof the wells (Figure
30).
30
~
!
z 1S
~
;
z
Figure 30. Nitrate-N concentrations (mg/l) in wells S2-22, ENG-SDC, MCD-SD,
and ZAK-SD, located downgradient of septic system drainfields.
107
Detailed Septic SystemsInvestigation
Detailed site evaluationwas conductedat Site REE in an attempt to better
identify groundwaterimpact from individual septic systems. Details of this
investigationcan be found in Master of ScienceThesis of William VanRyswyk, 1993.
Figure 31 showsthe monitoring well network installed at the REE site, along with
averagenitrate-N concentrationsfor eachwell.
From this figure alone it is obvious the initial wells (REE-SD and El) were not
in the contaminantplume, even though they both contain shallow well ports
N
I~CALE
15 meters
x Single
I
depth Skl...lng
+
(g1.~~
CII screen
B:>Nest of 3 _lis
. ~Itlport
RSD5-A
RSD5-8
RSDS-C.
RSD5-D
RSD5-E
.
.
19
11;~
18
11 25 23
11 18 17
6 11
2
2
well
.
.
13
11 11
6
15
11 5
12 1
5
3
3
Figure 31. Location of wells at Jordan Acres septic site REE, with average
nitrate-N concentrations (mg/i).
108
downgradientof the drainfield. The contaminantplume was found to be primarily
located near well nest REC, with most of the effluent entering the soil and aquifer at
the west end of the drainfield. This phenomenonis not uncommonin hignly
permeablesoils as reported by Reneauet al (1989).
To determinethe dispersionof the plume with distance,a seriesof five multiport
wells were installed 38 metersdowngradientfrom the drainfield in the summerof
1989. Data from thesewells are presentedin Figure 32, which showsthe
configuration of the contaminantplume 38 metersfrom the drainfield.
Figure33 showsthe watertablefluctuationat SiteREE, andFigure34 showsthe
nitrate-N concentrationsin the shallow, medium, and deepwells located 6 meters
downgradientof the drainfield. The wells have 30 cm screensspaced45 cm apart.
E
-/-
G*
~.
.
.
.
.
.
,
.
.
".
22
23
ft
.
.
~
. . .
. .
1
':
21
.'.,..-,:
I
.
20 ft
'
!/'"
19 ft',
0
" "
"r'...'
'.
ft::::::::::~:'~:.1~~~:::
ft
6 I
I
"2 i"
"
"""I"
2 1
- "'"J:
24
B
-11T-
-
r
-;
A
1
:
010~0.
I
.1.. . . .
.19-. ~.. . ..i
181"1 " " . .
I . ..
JJ. . 1..
25
18
14
12 . iI 000. .
3.4.. .I... ..1 I 0..
!
I
23- . 4.. . ..1 00.. j 0 oo,:~
i. I
.
...
.1. ..
. .
:1:1.. I
,
1..
,..
ft
;"
--".!:".
:~'.:'
44
j.oooo
:
.13.
r/
t"..
I ."
t...
BB
CC
*
.,,'./
:,
15 I
01010 OJ 0000.
,~:,.'
3.00...
r.
. . oS
{ ...........
BB
-4
.
-1
~ 0 OJ. . . . . . .
AA
AA
-:::-tC
/F'"
/
I
= 20.1
= 1.8
=
meters
(68
ft.)
meters
(6 ft.)
0.46
or
030
meters
Nltrate-N
estimated
Estimated
boundary
(1 or
1.5
ft.)
to be 6 moll
of
contaminant
for
these
zones
plume
Figure 32. Averagenitrate-N concentrationsin RSDSmultilevel wells 38 meters
downgradientof the REE drainfield.
10Q
10976
1.0974
1.0972
'"'
1.097
u
z
10968
+'
--
0
'"'
1
I~
W
'U
c
"
10964
~
~ 10962
-
In
I~ U
ii!
0966
1096
10958
1.0956
1.0954
1.0952
1.095
Figure 33. Watertable elevations as measured in well REC-Medium. Dashed line
represents screen bottom elevation of well REC-Shallow.
The fact that the well closestto the water table generally had the highest nitrate-N
concentrationdemonstratesthat the contaminantplume is quite thin within 6.6 m of
its source. A temporary drop in nitrate-N concentrationsfollowed the pumping of the
septic tank and a one week vacation by the residentsin Sept. 1990, illustrated by a
rapid changein groundwaterquality following this reducedloading (Figure 34).
Seasonalmovementof the contaminantplume toward the west was documented
by increasedconcentrationsof nitrate-N in monitoring well REW. The movementis
attributed to heavy use of the private well, which only occurred during periods of
irrigation (Figure 35). This well is locatedbetweenthe private well and well REC
(which was consistentlyin the plume). Similar shifts in plume location likely occur
throughout the subdivision and may accountfor someof the variability found at other
monitoring sites,
The data from the wells near the drainfield and 38 metersdowngradientof the
drainfield clearly show the contaminantplume remaining very narrow as it moves
110
90
80
70
-
60
~
so
'(T)
~
40
Z
30
20
10
0
Figure 34. Nitrate-N concentrations for REC-Shallow, Medium and Deep ports.
The effects of the septic tank pumping are apparent for several weeks after the
pumping event.
60
50
r\
40
g
u
Z
I
'"
30
~
20
0
Figure 35. Well REW located 4.9 meters downgradient of a drainfield. NitrateN concentrations increase in May, June, July and August corresponding to
irrigation well pumping resulting in changesin the plume configuration.
111
away from its source. A meannitrate-N concentrationof 48.4 mg/l at well REC-
Shallow, comparedto 24.9 mg/l for the most impactedwell 38 metersdowngradient
of the drainfield, showsa 50 percentreduction due to dispersionand mixing with low
concentrationsof nitrate-N in upgradientrechargewater. Maximum nitrate-N
concentrationsof 70 mg/l in well REC comparedto an averagetotal nitrogen
concentrationof 79 mg/l in the septic tank suggestsminimal nitrogen is removedby
the drainfield and shallow aquifer. Comparingtotal nitrogen to chloride ratios in the
septic tank to thosein the contaminantplume also indicateslittle if any nitrogen
removal. Concentrationsof sevensamples(collectedfrom the septic tank in 1991 and
the first half of 1992) averaged79.3 mg/l total nitrogen and 53.3 mg/l chloride, with
a meanratio of 1.5. This is very similar to the 1.4 nitrogen:chlorideratio found for
well at REC-Shallow, indicating little if any denitrification at this site. A slight
lowering of the ratio to 1.2 at RSDS-Cwas not found to be a statistically significant
changewith the Kouskan-WakisTest, and may be due to mixing in the aquifer rather
than chemical or biological changes.
Estimateswere madeof the total massof nitrogen entering the drainfield and
presentin the downgradientnetwork of monitoring wells (Figure 32). Details of the
analysisare presentedin VanRyswyk (1993). Thesecalculationsestimatedthe total
annualper capita nitrogen loading to the drainfield to be 5.5 kg/capita/year. The
weighted averagenitrate-N in the plume at the RSDS wells times a flow rate of 0.3
and 0.5 meters/day,gives a range of 9.6 to 14.4 kg nitrate-N flowing in this plume
38 metersdowngradientof the drainfield. This results in a range of 4.8 to 7.2 kg
nitrate-N/capita/year. Similarly, multiplying the maximum concentrationsof nitrate-N
112
in groundwateradjacentto the drainfield by the per capita water use gives a value of
5.5 kg/capita/year. All the valuesare in good agreementand within the range of 3.2
to 8.0 kg/capita/yr reported by Gold et al (1990) and Walker et al (1973 II). They
are also all in the range of values found by Shaw and Turyk (1992).
,,~
K. PhosphorousImpacts on Groundwaterfrom SepticSystems
Data presentedin Table 15 (page 106) show an increasein chemicalsother than
nitrate-N downgradientof septic systems. The presenceof thesechemicalsis useful
in tracking septic systemimpacts, and was particularly useful in this study in
determining the part of the aquifer downgradient of the septic systemsthat was
impactedby septic systemsrather than lawns or other sources,
Phosphorousdata presentedin Table 15 and Figures 24 and 28 (pages98 and
101) showing elevatedconcentrationsin downgradientmultiport monitoring wells in
Village Green and Jordan Acres indicate a significant impact of phosphorouson
groundwaterquality. Thesedata clearly indicate that the sandysoil presentin these
subdivisionscan becomesaturatedwith phosphorouswithin 20 years of septic system
use, thereby allowing high concentrationsto reach the aquifer five metersbelow
drainfields.
Site BAR had an additional multilevel well (KEP) installed 29 meters
downgradientof the septic system The well KEP-MED averages5.0 mg/l
phosphorousand 41 mg/l nitrate-N. Phosphorousvaluesin the wells downgradientof
the subdivision, as shown in Figures 24 and 28, show elevatedconcentrationsin the
shallower well ports, as compared to deeper wells (which sample groundwater that
originatesupgradientof the subdivision). These data indicate that phosphorus can be
transported a fairly long distance, which would be important if these subdivisions
were located near lakes. Under theseconditionslakes could be subjectedto the
eutrophying effects of high phosphorus loading from groundwater.
114
L. Variability of GroundwaterChemistry
Downgradient of Subdivisions Relative to Land Use
The variability of groundwaterchemistry both vertically and horizontally
perpendicularto the groundwaterflow was documentedby use of a number of
multilevel monitoring wells locateddowngradientof Village Green. Average
groundwaterdata for the downgradientmultiport wells are presentedin Figure 36.
Figure 4 (page34) showsthe location of the Village Green wells relative to
groundwaterflow, and the land use in that subdivision. The water chemistry of
groundwaterdowngradientof the subdivisionis obviously quite variable both
horizontally and vertically. The upper three sampleports at well W A2 are
particularlylow in nitrate-N,comparedto otherwells only 17 metersaway. We
believe the concentrationsof nitrate-N in theseports are lower becausethe recharge
that occurs over half the flow distanceof the subdivisionupgradientof this well is
from yards and road ditches, and few septic systemdrainfields. Wells WAI, S4 and
W A3 are believed to be samplinggroundwaterthat has rechargedin backyard areas
where most of the drainfields are located.
A similar wide range of nitrate-N concentrationswere found downgradientof the
Jordan Acres subdivision, as shown in Figure 36. For interpretive purposes,the
locations of septic systemsand roads are not as convenientlysituatedas in Village
Green (Figures 3 and 36, pages33 and 118). It is obvious that somewells intercept
contaminantplumes while others miss the impact of drainfields almost entirely.
115
Village Green Subdivision
N4 WA4
326
324
-J
U) 322
6 320
c:
0
o+:.
ro
>
Q)
jjj
318
314
312
8
14
17
7
18
8
13
15
17 ,18
20
20
17
21
14
12
12
15
24
1
11
12
11
316
WA1
17
18
23
6
12
13
10
20
54 WA2
,
'-6-
11
12
1
WA3
GROUND SURFACE
16
16
17
19
21
18
20
18
19
16
20
23
310
20
22
19
16
Jordan Acres Subdivision
,
334
--I
cn
332
10
330
~
328
c:
0
",p
CO
>
326
Q)
w
9
324
322
7
7
3
]'
7
7
7
8
6
'--53"-'--1
7
' 32
8
- 8
- 6
-
4
E4
E3
LIP
JCW3
GRE
A GROUND SURFACE
6
8
6
8
2
8
0.3
3
0.3
0.2
~---,
~ 3
i
3
2
1
1 2
E5
-.'-
~
6
7
11
4
12
5
8
5
9
5
8
320
Figure 36. Profiles of average nitrate-N concentrations (mg/l) in wells located
downgradient of the subdivisions. View is generally perpendicular to
groundwater flow.
116
7
3
.
Green
Land
-
LAND USES
Pav.m.nl
§
Lawn.
m
m
em
.
1
on
Use
~Grolnl..ler
BuIldinG.
CJ
VIS
N
FI,.
me ler I
Nalura\
Far..l.d
Gra..
0
'J0 0
Land.
Canopy
Clfltlflphtf:
Jp f i [
KID"
Tlf'.
1111
Figure 37. Map showing land uses of
117
.
V1
Land
LAND USES
Gronnl'altr
Pavem.,,\
§
Lawns
m
Na\ural
-
f"o
!'10,
N
Grass
l.d
land.
'\
Canopy
Clrl,crlphtr:
Ipril1983
Figure 38. Map showing land uses of Jordan Acres subdivision.
118
s10n
Use
BuIldings
0
.
Nlncy
rlryk
Theseresults lead to severalconclusionsrelative to groundwaterimpacts from
thesesubdivisions:
1 Water flow and contaminanttransportprocessesoccur with minimal mixing,
allowing for a high degreeof chemicalvariability in groundwater.
2. Septic systemscontribute larger amountsof nitrate-N to groundwaterthan do
lawns.
3..
From a practicalstandpoint,it is not feasibleto installa statisticallyvalid,
randomly placed monitoring network in a developedsubdivision; therefore, the
well locations for monitoring subdivisionimpacts needto be carefully chosen
to avoid overestimatingor underestimatingspecific impacts.
4
The use of shallow private wells in subdivisionswith onsite waste disposal
requires careful considerationof drainfield location and groundwaterflow
direction to prevent private wells from intercepting the contaminantplumes.
119
M. Water ChemistryChangesOver Time Downgradientof Subdivisions
Someof the multilevel wells usedin this study were sampledand analyzedover
a four year time period. During this time period, populationdensity and amount~of
groundwaterrechargevaried considerably. As discussedin SectionE, the amount of
groundwaterrechargecan have a large effect on nitrate-N concentrationsin
groundwaterwhen septic systemsare the major nitrate-N source. This is logical
becausenitrogen inputs to septic systemsremain relatively constantyear round and
from year to year, whereasthe amountof recharge(which varies) acts as the primary
dilution mechanism.Changesin land useover time canalsoleadto changesin
downgradientwater quality. Increasesor decreasesin population density, and
therefore wastegenerationare the major subdivisionland use practicesthat can cause
changesin downgradientwater chemistry. The BURBS model projection for low,
medium, and high septic systemdensity clearly show theseresults (Table 10 page
Figures 39 and 40 show the nitrate-N concentrationsfrom each well port of
monitoring well nestsN4 and S4 for the period of September1987 to April 1991.
Figure 17 (page76) showsthe precipitation amountsand the water table elevation for
well PAR during this time period. Thesefigures illustrate the degreeof chemical
variability that occurs in the shallowerports of the aquifer that samplegroundwater
originating from subdivisionrecharge. Well ports 22 through 40, sampling the upper
sevenmetersof the aquifer, show considerablevariability over time, comparedto
well ports 45 to 70, which sampledown to 23 metersbelow the land surface,
x
VG-N440
v VG-N450
0
VG- N4 60
<> VG-N4 70
~I
Figure 39. Nitrate-N concentrations (mg/l) of well N4 in Village Green, 1987 to
1991.
121
mOl
A
VG-S435
x
VG-S440
v
VG-S445
mOll
Figure 40. Nitrate-N concentrations (mg/I) of well S4 in Village Green, 1987 to
1991.
1?:?:
Nitrate-N values for the upper sevenmetersof the aquifer at S4, while showing
considerablevariability over time, do not show a long term trend of changingwater
chemistry. Wells samplingthe samewater depthsat N4 do show a definite increase
in nitrate-N concentrationsover this four year study period. The primary factor
contributing to this difference is the increasingamount of developmentupgradientof
N4 during and in the s~venyearsprecedingthe study. Most of the lots upgradientof
S4 were developedat least ten years before the start of the study and their impact
would have reachedthe downgradientwell nestsbefore the study began.
Shallow well ports in both well nestsshow steepincreasesof nitrate-N from
1987 to 1988. Most of this increaseis attributed to the fact that for severalyears
precedingthe study there was abovenormal precipitation and groundwaterrecharge,
which causedthe groundwaternitrate-N to be relatively low. In 1988 there were
drought conditions and significantly reducedrecharge,which resulted in increased
concentrationsof nitrate-No Dropping water levels during this time period shown in
Figure 17 (page76), illustrate this effect. Increasedrechargein 1989-91(indicated
by a rise in the water table) is consideredto have causedgreater dilution of septic
effluent, thereby reducing nitrate-N concentrations.
Well S4-30 doesnot show the samedecreasein nitrate-N in 1989-91as the
shallower wells. This is attributed to a longer travel time for this water, which still
showsincreasesfrom the drought years, while shallower wells show the dilution of
more recent rechargeevents.
Thesedata illustrate the wide variety of nitrate-N concentrationsthat can occur
vertically, horizontally,andover time downgradient
from land usessuchas
123
subdivisions. Drawing conclusionsfrom a single samplefrom a single depth at one
point in time is virtually impossible. Use of carefully located multilevel wells, and
sampling for a number of years is essentialfor any soundconclusionsto be drawp
relative to subdivisionimpacts on groundwaterquality.
1/4
N. GeophysicalTechniques
Electrical Resistivity (ER) and Ground PenetratingRadar (GPR) were evaluated
for their potential value in locating plumes from septic systems. The consistent
geologic nature of the alluvial outwashsand, the relatively shallow watertable, and an
extensivemonitoring well network provided ideal conditions for such an evaluation.
If a geophysicaltechniquewas determinedto be effective at locating septic plumes in
the sandplain, it would be a useful tool for siting local private water supply wells,
and prove very useful for future hydrogeological investigations in the area.
ER was evaluated at two different septic systems where sufficient downgradient
spacewas available for the proper electrodespacing. The spacerequired by the
electrode configuration proved very limiting in the subdivision environment.
Although increasesin electrical conductivity approachingfive times that of
background were measured in groundwater at one of the sites, the narrowness of the
septic plume as compared to the required electrode spacing likely resulted in non.
impactedareasmasking the affect of the impactedzone, Interferencesfrom
underground and overhead utilities (prevalent throughout the subdivision) also made
interpretation of the measuredresistancereadingsvery difficult. It was concluded
that ER was of limited value for locating septicplumes in the subdivision
environment.
GPR was evaluated at the Jordan Acres septic study site where the downgradient
septicplume was well defined, where the techniqueproved ineffective at locating the
edge of the septic plume. GPR was also evaluatedat severalnearby mound systems
where monitoring well networks were also installed. The depth to groundwaterin
125
this region was generally much shallower «
3.3 m) and the radar seemedto respond
with a reducedsignalover the plumeat oneor two of the sites,but resultslater
proved inconclusive. The groundwatercontaminantplumes from septic systems'4Ie
apparentlynot of sufficient strengthfor this techniqueto be effective, particularly in
areaswhere five to eight metersof unsaturatedsandsexist above the plume.
1?t:;
O. Trace Organic Chemical Investigation
A number of private wells, multiport monitoring wells and septic system
monitoring wells were sampledand analyzedfor volatile organic compounds(VOCs)
and polynuclear aromatic hydrocarbons(PAHs). Detailed results of thesestudiesare
reported in Henkel (1992).
Occurrenceof trace organic compoundsfrom septic systemdisposalwas
investigatedby installing monitoring wells to samplethe upper 0.9 m (3 ft) of
groundwaterdowngradientof, and within 9 m (30 ft) of drainfields. A total of five
systemswere evaluatedwhere the downgradientmonitoring wells interceptedthe
contaminantplume from the septic systems(Table 16).
Samplesfrom the five systemson threedateswereanalyzedfor VOCs. Four of
the five systemshad detectableVOCs presenton at least one sampledate. No sites
had VOCs presenton all three sampledates,illustrating the ephemeralnature of VOC
contaminationof groundwaterfrom householdpractices. The chemicalsfound, and
the measuredconcentrationsare presentedin Table 16.
Benzene,toluene, dichloroethane(DCA), trichloroethane(TCA), and
tetrachloroethylene(PCE) were identified in the groundwatersamples. Additional
peaks were occasionallypresent,but not in the group of chemicalsidentifiable by
EPA Methods 5030/601-602. Somedetectsof VOCs were found in private wells and
downgradientmonitoring wells, however the concentrationswere low and not
reproducible on subsequentsamplingdates. Occurrencesappearedto be localized and
in low concentrations.
1?7
Thesedata clearly indicate VOCs can reach groundwaterfrom household
chemical use and disposalinto septic systems. The ephemeralnature of occurrence,
and relatively low concentrationshelp minimize the health impact, however, more
significant concentrationsare possibleif larger quantitieswere disposedof by
homeowners.
PAR
VOC Analy~
WELL
Analy~
Oct
1988
Jan
ECD
Analym
TSD
Analys~
April
1989
Jan
1989
1989
April
1989
April
1989
April
1989
nd
2.53 BEN
nd
nd
+
+
nd
nd
nd
*
MCD-SUA
nd
MCD-SDB
nd
MOR-SUB
2.1 TOL
MOR-SDA
8.8DCA 2.4 DCA
21.6TCA 5.1 TCA
BAR-SUB
1.9 PCE
BAR-SDA
nd
nd
od
nd
*
+
BAR-SDC
nd
nd
nd
nd
bdl
*
KOP-SUB
nd
KOP-SDA
nd
bdl
+
AMD-SUA
2.4 TOL
AMD-SDB
nd
nd
*
2.17 BEN
nd
nd
nd
Resultsare p,g/l (parts/billion)
nd
chemical was not detectedin the sample
samplewas not analyzedfor that analyte
*
samplecontainednumerousand/or off scaleunidentified peaks
+
samplecontaineddetectableconcentrationsof that chemicalgroup
bdl
samplecontainedidentifiable PAH compoundsbelow the methoddetectionlimit
BEN
Benzene
TOL
Toluene
DCA
1,I-Dichloroethane
TCA
I, I, I-trichloroethane
PCE
1,1,2,2-tetrachloroethene
-
.
Table 16. Summary of organic chemicals detected in groundwater monitoring
well samples between October 1988 and April 1989.
128
Limited samplingand analysisfor PAHs did show somemovementof these
chemicalsto groundwater. PAHs with concentrationsless than one ppb were detected
in two wells downgradientof drainfields. Chemicalsidentified in thesetwo wells
were benzo(ghi)perylene,phenanthrene,gluoranthene,pyrene, and benzo(c)pyrene.
Many of thesechemicalsare found in householdproducts. The lack of groundwater
standardsfor thesechemicalsmakesit difficult to addressthe significanceof these
findings. Further researchon the presenceof thesechemicalsin groundwaterand
concentrationsdowngradientof septic systemsshouldbe conducted.
Other Organic Chemicals
A seriesof sampleswere collected from monitoring wells up and downgradient
of septic systemsand analyzedusing a methylenechloride extraction and gas
chromatographyanalysisusing electron capture (BCD) and thermoionic specific
detectors(TSD). This was done to determinethe relative abundanceof semi-volatile
chemicalsin groundwaterdowngradientof septic systemscomparedto groundwater
upgradientof the samedrainfields. Resultsfrom all five sites indicated the
occurrenceof a large number of unidentified organic chemicalsin groundwater
downgradientof drainfields, but few upgradient. Further researchusing GCMS is
neededto identify thesechemicalsand their concentrations.
The above seriesof analysesdemonstrateda wide range of organic chemicals
moving from the septic tank through conventionaldraintields to the groundwater
underlying thesesystems(at a depth of approximately7 metersand 7 meters
downgradientof the drainfield).
129
Potential Sources of the Detected Organic Compounds
The following information was compiled by Hathaway(1980) from the list of the
USEPA Priority Pollutantsand the householdproductsthey are commonly associated
VOCs are generally a componentof metal degreasers,solvents,and detergents.
Benzeneis found in adhesives,deodorants,paint solventsand thinners, and dandruff
shampoo. Toluene is commonly found in solvents,cleaningproducts, and cosmetics.
The compound ,l-dichloroethane (lIDCA) is a solvent found in degreasers;1,1,
trichloroethane(Ill TCA) is a solvent found in drain and pipe cleaners,oven
cleaners,degreasers,deodorizers,and photographicsupplies;and 1,1,2,2tetrachloroethene(PCB) is a solvent found in upholsteryand rug cleaners,contact
cement, degreasers,wax removers, and is a componentof pesticidesused in garden
sprays.
PAHs are common ingredientsof dandruff shampoos,eczemaand psoriasis
remedies,antibiotic creams,athletesfoot remedies,deodorants,insect repellents,
somedetergents,and are commonly usedin the manufactureof dyes. These
compoundswould likely be presentin drainfield effluent, but are generally
immobilized by particulate absorption,and (exceptfor naphthalene)are relatively
insoluble in groundwater(Verschueren,1983)
The BCD is sensitiveto a wide range of semi-volatilehalogenatedorganic
compoundssuch as pesticidesand PCBs. The TSD is selectively sensitiveto the
nitrogen and phosphorouscontaining semi-volatileorganic compoundssuch as those
found in many herbicides, Many chemicalsfound in householdproducts such as
chlorophenols,phthalates,and nitrobenzenescan also be detectedby these
instruments.
The abovelists are not complete,but rather,are a samplingof manycommonly
usedproducts that contain theseorganic compounds. Thesedata imply that the wells
with VOC, PAH, ECD, and/or TSD detectsare being impactedby residentia11and
use and/or septic systemdischarges.
131
P. Conclusions
1. Lawns and septic systemscontribute nitrate-N to groundwater,with septic systems
having a greater impact than lawns.
2. The BURBS massbalancecomputer model doesa good job of estimating
subdivision water and nitrogen massbalancesas long as the variables are well
defined for the subdivision.
3. Housingdensitiesof lessthan 1.1 to 1.7 dwellingsper hectarewere foundto be
neededto maintainnitrate-N concentrations
belowthe 10 mg/l standardin the
subdivisionsstudied.
4. In the sandy soil area of Central Wisconsin, using averagegroundwaterrecharge
of 24.6 cm per year and three peopleper householdwould require housing
densitiesless than 1.1 dwellings per hectare. Lower housing densitieswould be
neededin areaswith less groundwaterrecharge.
5. Mixing of subdivision-originatedgroundwaterwith that from upgradientsourcesis
minimal and occurs in someareasmore than others. This is apparentlydue to
effects of private wells and differential rechargewhich causelocal advectual
processes.
6,
Due to the rechargeof most of the runoff water from roads and roofs,
groundwaterrechargefrom within a subdivisionon sandy soils is considerably
greater than from adjacentfields and woods. This results in greater dilution of
septic systemcontaminants. The oppositewould be true in areaswhere most road
and roof runoff went to surfacerunoff rather than to groundwaterrecharge.
7
The amount of fluorescencein groundwaterwas generally a good indicator of
septic effluent and was useful in identifying water originating from within the
subdivision.
8. The ratio of sodium to chloride was useful in determining whether groundwater
originated from agricultural sources,the subdivision, or a highway right-of-way.
9.
Plumesfrom single or even a row of septic systemsshow minimal horizontal or
vertical mixing with groundwaterfrom other sources. Average reduction in
nitrogen content from septic tank to groundwateradjacentto drainfields is only on
the order of a two-fold dilution.
132
10.
Phosphorusconcentrationsfound in groundwaterdowngradientof four septic
systemsand two entire subdivisionsindicate that sandysoil can become
saturatedwith phosphoruswithin less than 20 years, and results in significant
leaching of even this generally immobile chemical. Concentrationsranging
from 1 to 11 mg/l were found downgradientof four septic systems.
1.
A limited number and relatively low concentrationsof VOCs were found in the
groundwaterassociatedwith subdivisionand septic systemmonitoring wells.
Thesechemicalscan and do get to groundwaterfrom homeowneruse, but
current levels of use and disposalof VOCs were low enoughto prevent any
high concentrationsfrom reachinggroundwaterunder the studied subdivisions.
12.
Well placementand depth of wells for homeownersin subdivisionsneedsto be
carefully consideredrelative to septic systemlocation and groundwaterflow to
prevent unwantedrecycling of wastewater.
133
Q. Literature
Cited
Alhajjar, B. J., G. Chesters,andJ. M. Harkin. 1990.Indicatorsof chemicalpollution
from septicsystems.GroundWater,28(4):559-568.
Alhajjar, B. J., J. M. Harkin, andG. Chesters.1989.Detergentformulaeffect on
transportof nutrientsto groundwaterfrom septicsystems.GroundWater,
27:209-219.
Anderson, D. L., J. M. Rice, M. L. Vorhees, R. A. Kirkner, and K. M. Sherman.
1987. Ground water modeling with uncertaintyanalysesto assessthe contamination
potential from on-site sewagedisposalsystemsin Florida. Proc. from the Fifth
National Symposiumon Individual and Small Community SewageSystems,December
14-15, 1987, Chicago, Illinois. 411 pp.
APHA, AWWA and WPCF, 1985. StandardMethods for the Examination of Water
and Wastewater.
Bauman,B. J. andW. M. Schafer.1984.Estimatinggroundwaterqualityimpacts
from on-sitesewagetreatmentsystems.Proc. of the FourthNationalHomeSewage
TreatmentSymposium.ASAE. pp 285-294.
Bicki, T. J., andR. B. Brown. 1991.On-sitesewagedisposal:The influenceof
systemdensityon waterquality.Journ.Eny. Health,53(5):39-42.
Bouma, J. 1979. Subsurfaceapplicationsof sewageeffluent. In M. T. Beatty et aI.
Planning the usesand managementof land. Agronomy, 21:665-703.
Bradbury and Bahr Methods-Monitoring well installation
Brown, K. W. and Associates.1980. An assessment
of the impact of septic leach
fields, home lawn fertilization and agricultural activities on groundwaterquality.
K. W. Brown and Associates,College Station, TX. 104 pp.
Cantor,L. W. andR. C. Knox. 1985.Septictank systemeffectson groundwater
quality. Lewis Publishers,Inc. 335pp.
Childs, K. E., S. B. Upchurch, and B. Ellis. 1974. Samplingof variable
waste-migrationpatternsin ground water. Ground Water, 12(6):369-377.
City of StevensPoint. 1991. Unpublishedprecipitation data from StevensPoint
WastewaterTreatment Plant, StevensPoint, Wisconsin.
1~.1
Clayton, L. 1986. PleistoceneGeology of PortageCounty, Wisconsin. University of
Wisconsin Extension, Wisconsin Geologicaland Natural History Survey, Info. Circ.,
56pp.
Cogger, C. G. 1988. On-site septic systems:The risk of groundwatercontamination.
Journ. Bny. Health, 51(1):12-16.
Cogger,C. G., andB. L. Carlile. 1984.Field performance
of conventionaland
alternativesystemsin wet soil. J. Environ.Qual. 13:137-142.
DeWal1e,F. B. andR. M. Schaff.1980.Ground-water
pollutionby septictank
drianfie1ds.
Journalof the Environmental
EngineeringDivision. 106:631-646.
Dudley, J. G. and D. A. Stephenson.1973. Nutrient enrichmentof ground water
from septic tank disposalsystems.Upper Great Lakes Regional Commission,Inland
Lake Renewaland ShorelandDemonstrationProject Rept., 131 pp.
Endelman,F. J., D. R. Keeney,J. T. Gilmour,andP. G. Saffigna.1974.Nitrate
andchloridemovementin a PlainfieldloamysandUnderintensiveirrigation. J.
Environ. Qual. 3:295-298.
Environmental Task Force, 1989, Unpublisheddata. University of WisconsinStevensPoint.
Faustini, J. M. 1985. Delineation of the GroundwaterFlow Patternsin a portion of
the Central SandPlain of Wisconsin. M.S. Thesis. University of Wisconsin-Madison,
Madison, Wisconsin. 117 pp.
Flipse,W. J., Jr. , B. G. Katz, J. B. Lindner,andR. Markel. 1984.Sourcesof
nitratein groundwaterin a seweredhousingdevelopment,
CentralLong Island,New
York. GroundWater,22(4):418-426.
Freeze,R. A., andJ. A. Cherry. 1979.Groundwater.PrenticeHall, Inc. Englewood
Cliffs, New Jersey07632.p.328.
Gold, A. J., W. R. DeRagon,W. M. Sullivan, and J. L. Lemunyon. 1990. Nitratenitrogen lossesto groundwaterfrom rural and suburbanland uses.J. Soil and Water
Cons., 45(2):305-310.
Hantzsche,N. N., and E. J. Finnemore. 1992. Predicting ground-waternitrateNitrogen impacts. Ground Water, 30(4):490-499.
Harmsen, E. W. 1989. Siting and Depth Recommendationsfor Water Supply Wells
In Relation to On-Site Domestic WasteDisposal Systems.Ph.D. thesis, University of
Wisconsin-Madison,Madison, Wisconsin.
135
Hathaway,S. W. 1980. Sourcesof toxic compounds
in householdwastewater.
EPA-600/2-80-128.U.S. EnvironmentalAgency,Cincinnati,OH, 45268. 83pp.
Henkel, S. 1992. The Impact of subdivisionson groundwaterquality in the Central
Wisconsin SandPlain; VOC contamination.M.S. Thesis. University of WisconsinStevensPoint, StevensPoint, Wisconsin.
Holt, C. L. R., Jr. 1965.GeologyandWaterResources
of PortageCounty
Wisconsin.U.S. GeologicalSurveyWaterSupplyPaper1796.77 pp.
Hughes,B. F. andS. Pacenka.1985.BURBS;A Simulationof the NitrogenImpact
of ResidentialDevelopmenton Groundwater.Centerfor EnvironmentalResearch,
CornellUniversity.Ithica, New York.
Jonas,J. D. 1990.Comparative
Toxicity of SelectedPortageCountyWells. M.S.
Thesis.Universityof Wisconsin-Stevens
Point, StevensPoint, Wisconsin.35 pp.
Katz, B. G., J. B. Lindner, and S. E. Ragone. 1980. A comparisonof nitrogen from
seweredand unseweredareas,NassauCounty, New York, from 1952 through 1976.
Ground Water, 18(6):607-616.
Kimball, C. G. 19~3. The Thermal, Chemical, and Physical Effects on the
Hydrogeologic Systemin the SandPlain of Wisconsin from Water SourceHeat Pump
Dischargevia a Return Well. M.S. Thesis. University of Wisconsin-Madison,
Madison Wisconsin.
Kolega,J. J., D. W. Hill, andR. Laak. 1986. Contributionof toxic chemicalsto
groundwaterfor domesticon-sitesewagedisposalsystems.NationalTechnical
InformationService,Springfield,VA, 22161. 38 pp.
Kraft, G. J., andP. A. Helmke.1992.Dependence
of aldicarbresiduedegradation
rateson groundwaterchemistryin the WisconsinCentralSands.J. Environ. Qual.
21:368-372.
Kuo, S. and Mikkelsen. 1979. Distribution of iron and phosphorusin flooded and
unflooded soil profiles and their relationshipto phosphorusadsorption. Soil Science,
127:1.
Laak, R. 1974. Nitrogen and phosphorusremoval in a septic tank and a lagoon.
Experimentalinvestigationof nitrogen and phosphorusremoval at the University of
ConnecticutResearchStation. University of Connecticut,Storrs, Connecticut.
Laak R., K. A. Healy, andD. M. Hardisty.1975.Rationalbasisfor septictank
systemdesign.GroundWater, 12(6):348-351.
1~~
Lance, J. C. 1977. Phosphateremoval from sewagewater by soil columns. J,
Environ. Qual. 6:279-284.
Leonard, L. 1986. Application of a computer modeling techniquefor understanding
groundwaterimpacts associatedwith residentialdevelopment,unpublishedmanuscript.
Center for Land Information Studies,University of Wisconsin-Madison,Madison,
Wisconsin.
Manser, R. J. 1983. An Investigationinto the Movement of Aldicarb Residuesin
Groundwaterin the Central SandPlain of Wisconsin. M.S. Thesis, University of
Wisconsin-Madison,Madison, Wisconsin.
Mechenich, C. 1988. Nitrate in Wisconsin's drinking water-What is its human health
significance. Literature rev,iewfor UW-Extensionfaculty. Central Wisconsin
GroundwaterCenter, StevensPoint, Wisconsin.
Mechenich,C., B. H. Shaw,P. Nowak,andF. Madison1991. ChemicalUseand
AttitudesaboutGroundwaterin Two PortageCounty,WisconsinSubdivisions.
CentralWisconsinGroundwater
Center,StevensPoint, Wisconsin.
Morton, T. G., A. J. Gold, and W. M. Sullivan. 1988. Influence of over watering
and fertilization on nitrogen lossesfrom home lawns. J. Environ. Qual., 17(1):124130.
Nagpal, N. K. 1986. Effect of soil and effluent characteristicson phosphorussorption
in dosedcolumns. J. Environ. Qual. 15:73-78.
Noss, R. R. and M. Billa. 1988. Septicsystemmaintenance
management.J. of
Urban Planning and Development, 114(2):73-90.
Noss,R. R. 1989. Septicsystemcleaners:A significantthreatto groundwater
quality.Joum. of Env. Health,51(4):201-204.
Office of Technology Assessment.1984. Protecting the nation's groundwaterfrom
contamination.U.S. Congress,Washington,DC. Report No. OTA-O-233.
Osborne,T. 1988. Unpublisheddata. Central Wisconsin GroundwaterCenter,
University of Wisconsin, StevensPoint, Wisconsin.
Owen,T. R., andD. Barraclough.1983. The leaching of nitrates from intensively
fertilizedgrassland.Fert. Agric. 85:43-50.
Pell, M. and F. Nyberg. 1985. Kvavereduktion.In: BromssenU. (ed).
Avloppsinfiltration, Naturvardsverket,Minab/Gotab, Stockholm, Sweden.
137
Perkins,R. J. 1984.Septictanks,lot sizeandpollutionof watertableaquifers,
Joum. of Env. Health,46(6):298-304.
Petrovic,A. M. 1990.The fate of nitrogenous
fertilizersappliedto turf grass.J
Environ. Qual. 19(1):1-14.
Pitt, W. A. J., Jr., H. C. Mattraw,andH. Klein. 1975.Groundwaterqualityin
selectedareasservicedby septictanks,DadeCounty,FL. U.S. GeologicalSurvey
OpenFile ReportNo. 75-607.Tallahassee,
FL. 82 pp.
Quan,E. L., H. R. Sweet,andJ. R. Illian. 1974.Subsurface
sewagedisposaland
contamination
of groundwaterin EastPortland,Oregon.GroundWater, 12(6):356367.
Rea, R. A. and S. B. Upchurch. 1980. Influence of regolith propertieson migration
of septic tank effluent. Ground Water, 18(2):118-125.
Reneau,R. B. 1979. Changein concentrationof selectedchemicalpollutants in wet,
tile-drained soil systemsas influencedby disposalof septic tank effluents. J.
Environ. Qual., 8(2):189-195.
Reneau,R. B., C. Hagedorn, M. J. Degen. 1989. Fate and transport of biological
and inorganic contaminantsfrom on-site disposalof domesticwastewater.J. Environ.
Qual., 18:135-144.
Reneau,R. B., andD. E. Pettry. 1976.Phosphorus
distributionfrom septictank
effluentin coastalplain soils.J. Environ.Qual., 5(1):34-39.
Rieke,P. E., andB. G. Ellis. 1974.Effectsof nitrogenfertilizationon nitrate
movementunderturf grass.p.120-129.In E. C. Roberts(ed.)Proc. Int. Turf. Conf.,
2nd. Blacksburg,Va. 19-21june, 1973.ASA, MadisonWisconsin.
Robertson,W. D., J. A. Cherry, and E. A. Sudicky. 1991. Ground-Water
contaminationfrom two small septic systemson sandaquifers. Ground Water,
29(1):82-92.
Rothchild, E. R. 1982. Hydrogeology and contaminanttransport modeling of the
Central SandPlain, Wisconsin. M.S. Thesis. University of Wisconsin-Madison,
Madison, Wisconsin.
Sawhney,B. L. 1977. Predicting phosphatemovementthrough soil columns. J.
Environ. Qual. 6(1):86-89.
Shaw, B. H. 1985. Guide to interpreting inorganic water quality data for drinking
water. University of Wisconsin-StevensPoint.
138
Shaw, B. H. 1988. Phosphatedetergentdocumentreview. Written correspondenceto
G. Chesters.University of Wisconsin-StevensPoint.
Shaw,B.H. andN. T. Turyk 1992. A Comparative
Studyof Nitrate-NLoadingto
Groundwaterfrom Mound,In GroundPressure,andAt GradeSepticSystem.
Universityof Wisconsin-Stevens
Point.
Small ScaleWaste ManagementProject. 1978. Managementof small waste flows.
University of Wisconsin-Madison.EPA-600/7-78-173.
Stoertz,M. W. 1985.Groundwaterrechargeprocesses
in the CentralSandPlain of
Wisconsin.M.S. Thesis.Universityof Wisconsin-Madison,
Madison,Wisconsin.
Tinker Jr., J. R. 1991. An analysisof nitrate-nitrogen
in groundwaterbeneath
unsewered
subdivisions.GroundWaterMonitoringReview,11(1):141-150.
Tomson,M., C. Curran,J. M. King, H. Wang,J. Dauchy,V. Gordy, andB. H.
Ward. 1984. Characterization
of soil disposalsystemleachates.EPA-600/2-84-101.
U.S. EnvironmentalProtectionAgency,Cincinnati,OH, 45268. 76 pp.
u.s. EnvironmentalProtectionAgency.1977.The ReportTo Congress-Waste
DisposalPracticesAnd Their EffectsOn Groundwater.U.S. EPA, Washington,DC.
U.S. Environmental Protection Agency. 1980. Design Manual-an-Site Wastewater
Treatment and Disposal Systems.U.S. EPA Rep. 625/1-80-012.U.S. EPA,
Washington, DC.
VanRyswyk,W. S., 1993. An Evaluationof ConventionalSepticSystemsandtheir
impacton GroundwaterQualityin the CentralWisconsinSandPlain, M.S. Thesis
(draft). Universityof Wisconsin-Stevens
Point, Stevens.Point,Wisconsin.
Verschueren,Karel, 1983. Handbookof EnvironmentalData on Organic Chemicals,
2nd ed. VanNostrandReinhold Co. NY.
Vigel, J., S. Warburton, W. S. Haynes, and L. R. Kaiser. 1965. Nitrates in
municipal water supply causemethemoglobinemiain infant. Public Health Reports,
80(12):1119-1121.
Viraraghaven, T. 1985. Temperatureeffects on on-site wastewatertreatmentdisposal
systems.Journ. Env. Health, 48(1):10-13.
Viraraghaven,T. andR. G. Warncock.1976.Groundwater
pollutionfrom a septic
tile field. Water, Air, andSoil Pollution,5:281-287.
1~q
Walker, W. G., J. Bouma, D. R. Keeney, and F. R. Magdoff. 1973. Nitrogen
transformationsduring subsurfacedisposalof septic tank effluent in sands:I. Soil
transformations.J. Environ. Qual., 2(4):475-480.
Walker, W. G., J. Bouma, D. R. Keeney, and P. G. Olcott. 1973. Nitrogen.
transformationduring subsurfacedisposalof septic tank effluent in sands:II. Ground
water quality. J. Environ. Quality, 2(4):521-525.
Weeks, E. P. 1969. Determining the ratio of horizontal to vertical permeability by
aquifer test analysis. Water ResourcesResearch,5(1): 196-214.
Weeks, E. P., D. W. Erickson, and C. L. R. Holt, Jr. 1965. Hydrology of the Little
Plover River Basin PortageCounty, Wisconsinand the Effects of Water Resource
Development.United StatesGeological Survey, Water Supply Paper 1811, 77 pp.
Weeks, E. P., and Stangland.1971. Effects of irrigation on streamflow in the
Central SandPlain of Wisconsin. U.S. Geological Survey Open File Rep. 113 pp.
Wehrmann, A. 1983. Potential nitrate contaminationof groundwaterin the Roscoe
Area, WinnebagoCounty, Illinois. SES Contract Report 325. Illinois Dept. Of
Energy and Natural Resources-State
Water Survey Division, GroundwaterSection.
p.58.
Whelan,B. R. 1988.Disposalof septictankeffluentin calcareous
sands.J. Environ.
Qual. 17:272-277.
Yates,M. V. 1985.Septictankdensityandground-watercontamination.
Ground
Water,23(5):586-591.
Yates, M. V. and S. R. Yates. 1989. Septic tank setbackdistances:A way to
minimize virus contaminationof drinking water. Ground Water, 27(2):202-208.
140